This patch may be a little misleading in terms of size
since most of the changes just reorder a little logic.
The most significant changes involve two GUEST values.
My original implementation excluded such tics from the
TOTAL calculation and, therefore, the BUSY figure too.
That decision was erroneously based on some code found
in ./kernel/sched/cputime.c which in hindsight applies
only to processes, not those system level cpu figures.
[ another likely oops classified STOLEN tics as IDLE ]
So, this patch attempts to bring those SUM values into
better agreement with the calculations performed for a
root cgroup (see ./kernel/cgroup/rstat.c source file).
[ we differ from those above in that we also include ]
[ the IDLE plus IOWAIT tics in our TOTAL calculation ]
Signed-off-by: Jim Warner <james.warner@comcast.net>
There's a huge toe-stubber awaiting future maintenance
as reflected in that commit below which deals with the
addition of new enumerators to the Item_table. Namely,
whenever the table is grown, one must remember to also
change that existing 'logical_end' enumerator's value.
Well, not anymore! Since that MAXTABLE macro was added
to the procps-private.h header we can now also exploit
it so a 'logical_end' automatically tracks table size.
This change also renders some code associated with the
ITEMTABLE_DEBUG #define unnecessary. So it's gone too.
Reference(s):
. 08/2016, add new enumerators
commit 09e1886c9e
. 08/2020, added MAXTABLE macro
commit c865b06c30
. 08/2020, introduced ITEMTABLE_DEBUG
commit 92d0297e1e
Signed-off-by: Jim Warner <james.warner@comcast.net>
At 'new' time, the major API modules each ensure their
'info' parameter isn't NULL but what it pointed to was
except this single straggler, for some unknown reason.
So, this patch brings him into line with those others.
[ And, without going into the ugly details, this was ]
[ the reason I never experienced an abend originally ]
[ but Craig did. And, though related to stacks mgmt, ]
[ zero initialization was not a factor. Anyway, with ]
[ this patch, everybody would have experienced abend ]
[ under the original (faulty) test_Itemtables logic! ]
Reference(s):
https://www.freelists.org/post/procps/keep-on-patchin,13
Signed-off-by: Jim Warner <james.warner@comcast.net>
Me thinks Craig had the right idea but perhaps not the
most correct solution. As currently structured, all of
the tests now go way too far by checking every 'unref'
and 'new' call when what we're trying for is survival.
In the final analysis, it doesn't matter who issues an
EXIT_FAILURE - that run_tests guy or an early Exit out
of a procps_new() function. They both will produce the
same end result of the desired "FAIL" test diagnostic.
[ and this patch once again allows the slabinfo test ]
Reference(s):
commit 4eeed6dcff
Signed-off-by: Jim Warner <james.warner@comcast.net>
The referenced commit introduced a test program for the API
but it would often fail due to:
The given pointer for _new() not being NULL
The return value for _new not checked, so the subsequent _unref()
would free() random memory
slabinfo checks failing due to permission denied errors.
The first two are fixed, as well as returning a fail to the test
if they don't return correctly, with slabinfo waiting to see if there
is a way of initialising the structure without reading the slabinfo.
References:
commit e616409aa4
Signed-off-by: Craig Small <csmall@dropbear.xyz>
This change sets the stage for exploiting the recently
added ITEMTABLE_DEBUG #define. All tests are performed
in a single module (after trying 6 separate programs).
The chances of each test detecting errors is extremely
remote (at least while I'm maintaining these modules).
However, this single program approach has one flaw and
it relates to the response whenever an error is found.
Each of those six new API modules calls Exit() if they
detect an error. Otherwise, incorrect results would be
produced at the least or an abend encountered at most.
This means that multiple 'make check' invocations will
be needed if more than 1 module actually was in error.
All in all, it is a small price for a large assurance.
Reference(s):
https://www.freelists.org/post/procps/keep-on-patchin,7
Signed-off-by: Jim Warner <james.warner@comcast.net>
The recent work on updating the <meminfo> and <vmstat>
modules with some newly added linux fields reminded me
(again) of a need for some mechanism guaranteeing that
a header file agrees with the source file assumptions.
Sadly, in the past, if a table entry was omitted or if
the table and header are ordered differently, then the
library would silently return the wrong results values
or even potentially experience a SIGSEGV abnormal end.
This patch offers a much needed development assist for
ensuring that Item_table entries are synchronized with
header file enumerators in terms of number plus order.
It's intended solely for our use as libprocps evolves.
Now, by activating ITEMTABLE_DEBUG, either directly or
via ./configure CFLAGS='-DITEMTABLE_DEBUG', the number
and order will be verified. It is envisioned that this
feature will be used at least once prior to a release.
Signed-off-by: Jim Warner <james.warner@comcast.net>
This macro should help the following patch be a little
less prolix. Besides, this private header could/should
do just a little more to help with our newlib efforts.
Signed-off-by: Jim Warner <james.warner@comcast.net>
This cosmetic change just prepares for the later patch
introducing validation of Item_tables and enumerators.
[ and, we'll now have better 'set' function names of ]
[ 'set_diskstats_ENUM' instead of the more redundant ]
[ current 'set_diskstats_DISKSTATS_ENUM' convention. ]
[ now our only exception is the <slabinfo> api where ]
[ a full enumerator identifier with 'SLAB' & 'SLABS' ]
[ prefixes are used, and 'SLABINFO_noop/extra' guys. ]
Signed-off-by: Jim Warner <james.warner@comcast.net>
Since last visited, there have been several new fields
added and one field deleted in the /proc/meminfo file.
[ references shown below represent linux git commits ]
Reference(s):
. 4/2020, added 'ShadowCallStack'
commit 628d06a48f57c36abdc2a024930212e654a501b7
. 9/2019, added 'FileHugePages' & 'FilePmdMapped'
commit 60fbf0ab5da1c360e02b7f7d882bf1c0d8f7e32a
. 9/2019, removed 'Quicklists'
commit 13224794cb0832caa403ad583d8605202cabc6bc
Signed-off-by: Jim Warner <james.warner@comcast.net>
This commit attempts to smooth some wrinkles impacting
any future libprocps user exploitation. The 2 problems
relate exclusively to our XTRA_PROCPS_DEBUG provision.
1. The 'xtra-procps-debug.h' header had an include for
'procps-private.h', which was not an installed header.
So the STRINGIFY macros will now be embedded directly.
2. Each of the new api headers referenced '<proc/...>'
rather than '<procps/...>' for the debugging #include.
So, we must drop that prefix in favor of a quoted file
name so that debugging builds work regardless of where
that 'xtra-procps-debug.h' header happens to be found.
Reference(s):
. Jun, 2020 - changed target install directory
commit d64755ea5f
. Sep, 2018 - #include migrated from procps.h
commit fab37662ef
Signed-off-by: Jim Warner <james.warner@comcast.net>
I almost feel like I should apologize for this kind of
patch ( *almost* ). But, since this comment was unique
to the <pids> api and since it was especially designed
to align with the following comment and since the next
comment already carried the alignment emphasis, I will
refrain from issuing any apology and submit it anyway.
[ plus to prove that i am not totally anal-retentive ]
[ and can exercise some restraint there are two more ]
[ places where i COULD have added alignment emphasis ]
[ see lines 804-806 and lines 1360-1361 for my proof ]
Signed-off-by: Jim Warner <james.warner@comcast.net>
This patch just trades the 'typestr' for the much more
meaningful 'valid range' when a relative enum has been
deemed invalid under that XTRA_PROCPS_DEBUG provision.
[ and we'll also make one comment a bit more generic ]
Signed-off-by: Jim Warner <james.warner@comcast.net>
In that commit referenced below, a promise was made to
revisit an 'escape_str' function in efforts to make it
private to the library. The problem was it's needed by
both ps plus the library which is why it was exported.
So, in an effort to remove it from libprocps.sym, this
patch duplicates all the required code in ps/output.c.
Now, each version can be made private to their caller.
[ along the way we'll use this opportunity to remove ]
[ the 'restrict' qualifiers from function parameters ]
[ while swatting a compiler warning referenced below ]
Reference(s):
. April 2016, most escape functions made private
commit d916d5db86
proc/escape.c: In function `escape_command':
proc/escape.c:182:23: warning: initialization of `const char **' from incompatible pointer type `char **' [-Wincompatible-pointer-types]
182 | const char **lc = (char**)pp->cmdline;
| ^
Signed-off-by: Jim Warner <james.warner@comcast.net>
There was a time when that procps.h file served a more
traditional role. Prior to the commit referenced below
it held just macros plus manifest constants. But, with
that change, such items were replaced with a series of
includes embracing all the library exported functions.
That approach was known to disguise errors which would
have otherwise yielded a compiler warning. And without
such a warning, there was no way to address the error.
So this patch will trade the all inclusive header file
approach for individual includes only where necessary.
Reference(s):
. April 2016, procps.h header file revamped
commit ccb6ae8de1
. Sept 2018, top abandoned use of procps.h
commit a6dfc2382e
Signed-off-by: Jim Warner <james.warner@comcast.net>
The meminfo & vmstat file read buffers are now defined
through symbolic constants next to the symbolic names.
[ recent attention to the /proc/stat buffer size led ]
[ to this (hopefully) better approach to definitions ]
Reference(s):
commit 81f4a6acdf
Signed-off-by: Jim Warner <james.warner@comcast.net>
We won't go as far as the merge request shown below in
increasing buffer size, but we will reduce by half the
total iterations while growing it to achieve one read.
[ and this seems in line with what was recently done ]
[ to help top under a massively parallel environment ]
[ thru 2 abreast ('4') and combined cpus ('!') modes ]
Reference(s:
https://gitlab.com/procps-ng/procps/-/merge_requests/105
Signed-off-by: Jim Warner <james.warner@comcast.net>
Now that we may be getting serious with documentation,
that stat module was revisited with an eye toward user
friendliness. Heck, even this author puzzled over some
of the existing notes and naming conventions employed.
So, this patch will adjust some identifiers and expand
the notes to (hopefully) better serve potential users.
The most significant change was making the STAT_TIC_ID
always valid for numa nodes, even if any are inactive.
Thus the -22222 special STAT_NODE_INVALID constant now
is applied only to STAT_TIC_NUMA_NODE. It will be used
on the cpu summary and reaps with STAT_REAP_CPUS_ONLY.
And it will also mark any numa node that was inactive.
Signed-off-by: Jim Warner <james.warner@comcast.net>
In preparation for a documentation attempt, this patch
renames 'struct reap' to 'struct reaped' in two of our
interfaces. That will bring all the non-pid interfaces
into agreement since the <stat> api already used that.
Signed-off-by: Jim Warner <james.warner@comcast.net>
Thanks to Konstantin for discovering 2 problems in the
issue referenced below. That 15+ year old logic went a
little too far overboard wrestling with a utf8 string.
Henceforth, we will not treat 'x9b' as special. And we
also will handle a 'combining acute accent' correctly.
Reference(s):
https://gitlab.com/procps-ng/procps/-/issues/176
Signed-off-by: Jim Warner <james.warner@comcast.net>
From http://man7.org/linux/man-pages/man5/proc.5.html:
(22) starttime %llu
The time the process started after system boot. In
kernels before Linux 2.6, this value was expressed
in jiffies. Since Linux 2.6, the value is expressed
in clock ticks (divide by sysconf(_SC_CLK_TCK)).
Well, shit! With release 4.0 on March 25th the lxc/lxd
folks have stuck it to us once again. They changed the
cgroup lxc prefix used to identify the container name.
Signed-off-by: Jim Warner <james.warner@comcast.net>
All TIC delta fields are checked for possible negative
results and set to zero when found. This is done so as
to protect against potential anomalies which depend on
kernel version and/or toggling cpus offline or online.
[ it's probably unnecessary with the latest kernels, ]
[ except for iowait. documentation suggests it might ]
[ decrease which would then create a negative delta. ]
The same approach is employed for most of the 'system'
deltas (ctxt, intr & procs_created). However, with two
of the fields (procs_blocked & procs_running) negative
results were allowed. But it now seems such a division
is unwise so this patch will allow all to go negative.
[ rather than force any 'system' delta value to show ]
[ what's logical, we'll now let all reflect reality. ]
Signed-off-by: Jim Warner <james.warner@comcast.net>
This patch just standardizes/normalizes the whitespace
employed within a couple of nearly identical #defines.
Signed-off-by: Jim Warner <james.warner@comcast.net>
Under newlib, the only caller of the readproc routines
is that pids module. And in every case, the address of
some static proc_t structure has always been provided.
As a result, there is no need for the logic supporting
calloc() for a possible NULL pointer which was present
in both of those readproc() and readeither() routines.
Additionally, that pids module takes ownership of most
dynamically acquired 'str' plus 'strv' memory whenever
assigning to a results structure. So, henceforth under
the free_acquired() guy we will only free those string
fields which might exist when not explicitly selected.
Signed-off-by: Jim Warner <james.warner@comcast.net>
This patch just eliminates a parameter present for the
simple_readtask() function which is not needed nor has
it ever actually been used. It will make calls to that
function (via taskreader ptr) slightly more efficient.
Signed-off-by: Jim Warner <james.warner@comcast.net>
When some cleanup was performed on the readproc module
in the commit shown below, some residual code involved
with the 'did_fake' flag remained. Since such logic no
longer served any real need, this patch will whack it.
Reference(s):
. cleanup of readproc functions
commit 887bb51016
Signed-off-by: Jim Warner <james.warner@comcast.net>
No libprocps user expects signal values to be returned
as 'long long' quantities. More importantly the <PIDS>
api only returns a 'str' result for signal categories.
So this patch eliminates all the conditional code that
depends on the absence of the #define 'SIGNAL_STRING'.
Signed-off-by: Jim Warner <james.warner@comcast.net>
This patch will just correct an oops introduced in the
commit shown below. Thank goodness both 'str' & 'strv'
occupy the same storage location in that result union.
Reference(s):
. standardize 'errno' management
commit 06be33b43e
Signed-off-by: Jim Warner <james.warner@comcast.net>
This patch just implements an equivalent to the master
branch 'CPU_ZEROTICS' provision. However, the original
impetus for that earlier implementation was ultimately
attributed to a likely kernel anomaly since corrected.
As a result, in this newlib implementation we take the
opposite approach to the default behavior. There is no
adjustment to TIC_SUM_DELTA values if fewer ticks than
expected are recorded, unless the define is activated.
The commit shown below explains why the 'CPU_ZEROTICS'
define was retained in spite of the fix to the kernel.
Reference(s):
. issue referencing CPU_ZEROTICS
https://gitlab.com/procps-ng/procps/issues/132
. master branch CPU_ZEROTICS summary
commit ee3ed4b45e
. lengthy thread leading to CPU_ZEROTICS
https://www.freelists.org/post/procps/CStates-handling-new-switch
Signed-off-by: Jim Warner <james.warner@comcast.net>
Some parts of our newlib implementation are the result
of functions which have been propagated from module to
module. In particular, those 'cleanup_stacks' routines
are all similar & likely originated in the <pids> api.
In that interface there was a need to free dynamically
acquired memory before the result structure was reused
to satisfy subsequent 'get', 'select' or 'reap' calls.
This, in turn, led to a concept of 'dirty' stacks with
the need to call one of two 'cleanup_stack' functions.
None of the remaining interfaces deal with such memory
yet they each had their own 'cleanup_stack' functions.
Those functions were responsible for resetting each of
the result unions to zero, excluding any 'noop' items.
The bottom line is that for all interfaces, repetitive
calls would require iterating through the stack(s) two
separate times: once to 'cleanup' another to 'assign'.
With this commit we will reduce iterations to just the
'assign' routine. A reset to zero will be accomplished
in the 'extra' item set routine (which is the only one
actually requiring any reset). All other items will be
reinitialized automatically by a new current set value
or upon reallocation when an items compliment changes.
In the <pids> interface, any freeing of dynamic memory
could have been accomplished by adding that 'freefunc'
check to the 'assign' function. However, that requires
an Item_table test with every item. Instead, we'll now
satisfy such needs as the very first step in those set
functions responsible for dynamically acquired memory.
[ the <pids> api retains 2 'cleanup_stack' functions ]
[ to accommodate stack(s) 'reset' & to serve 'unref' ]
Lastly, all the 'itemize_stack' functions were tweaked
by eliminating an unnecessary initialization of result
unions. That objective was already accomplished by the
calloc() in a 'stacks_alloc' function or the remaining
'cleanup_stack' routine found in the <pids> interface.
Signed-off-by: Jim Warner <james.warner@comcast.net>
These changes are an outgrowth of the research/testing
behind the previous commit. There is no commingling of
select/reap stacks in interfaces beyond the <pids> api
since there's no need to support any 'reset' function.
However, those <pids> changes prompted a review of all
interfaces offering that 'stacks_fetch' function, thus
revealing 2 instances of useless logic/wasted efforts.
Signed-off-by: Jim Warner <james.warner@comcast.net>
When the <pids> api was refactored in the commit shown
below, one objective was enabling the simultaneous use
of 'get' & 'select/reap' functions. Unlike other 'get'
functions, this <pids> 'get' acts as an iterator where
successive calls will return successive tasks/threads.
However, that goal wasn't quite met since a stack used
by 'get' was commingled with the 'select/reap' stacks.
Such commingling supported the 'reset' function, again
a provision which was unique to this <pids> interface.
Unfortunately, some poor assumptions in 'stacks_fetch'
produced a SEGV whenever 'reap/select' followed 'get'.
Thus, this patch addresses those issues and guarantees
such commingled stacks (extents) will be accommodated.
Reference(s):
. standardize portions of interface, <PIDS> api
commit 9ebadc1438
Signed-off-by: Jim Warner <james.warner@comcast.net>
The commit referenced below addressed (some) anomalies
surrounding 'strv' pointers. However, there remained a
couple quirks involving a potential NULL return value.
Any NULL values returned from the old library readproc
guys would cause no real harm for newlib. But they did
produce the misleading "[ duplicate ENUM_ID ]" result.
The following all represent potential NULL results and
suggest shortcomings in testing of that earlier patch.
. kernel threads do not have cgroup, cmdline & environ
. even if present environ could require root to access
So, this patch reverts a portion of the earlier commit
and ensures when some vectored string is not available
a traditional dash ('-') is the 'strv' returned value.
[ and we'll also correct one typo in the header file ]
Reference(s):
. eliminated a final potential NULL, <PIDS> api
commit 09503dc597
Signed-off-by: Jim Warner <james.warner@comcast.net>
This commit is intended as a refinement of the patches
mentioned below, where origins/sources of newlib items
were added to the header files for user documentation.
However, if those additions are to be truly effective,
along with kernel documentation (where available), the
following prerequisites must also have been satisfied:
. our identifiers closely align with linux field names
. our derived items are documented or self-documenting
Satisfying those prerequisites prompted this patch and
for these changes, kernel sources were emphasized over
available documentation (shame on me, it should always
have been so). And, while some 'new' fields were found
to be conditional, they were included unconditionally.
These changes appear more extensive than they actually
need be since I have attempted to enforce some spacing
conventions. So, I've summarize the significant things
in the sections that follow. For a proper perspective,
use: 'git diff --ignore-space-change' (good as alias).
___________________________________________ <PIDS> api
This api is unique in that there exists many different
file/directory origins subordinate to /proc/<pid>. And
our item identifiers are sometimes coerced so as to be
able to group related or similar enumerators together.
So, users needed more help relating our identifiers to
an actual documented field. Thus, we will now also add
the field names as with 'stat: delayacct_blkio_ticks'.
Each item ending with a '_C' now consistently includes
both the parent's count/time plus waited for children.
That 'RTPRIO' guy was renamed/relocated as PRIORITY_RT
since its original name is an implementation artifact.
___________________________________________ <STAT> api
The only api change was to correct a typo ('dervied').
_________________________________________ <VMSTAT> api
Even ignoring white space, this interface received the
largest number of changes. Mostly, this was because of
deficiencies in the proc(5) documentation. Recall that
this documentation already sorely lacks any substance.
Usually, just kernel releases are noted, not contents.
When compared to kernel source, that proc(5) contained
many non-existent fields and also omitted many others.
________________________________________ <MEMINFO> api
Sadly, with this api many of the changes were simply a
correction of some earlier 'human error' where several
fields where hashed then tracked but never represented
with an item enumerator in this meminfo.h header file.
_______________________________________ <SLABINFO> api
The 'SLABS' (summary) & 'SLABNODE' items were reversed
since the former are derived from the separate caches.
More significantly, those 'SLABNODE' guys were renamed
to 'SLAB' since they concern individual caches and the
concept of 'nodes' is really an implementation detail.
Also, several enumerators were changed to more closely
agree with official slabinfo(5) documentation referred
to in what we're treating as a base document: proc(5).
Lastly, while those 'SLABS' items are solely a product
of our library and not represented in slabinfo(5), the
names attempt to parallel those found as 'SLAB' items.
______________________________________ <DISKSTATS> api
One enumeration identifier was changed so as to better
reflect its relationship to that actual documentation:
'Documentation/iostats.txt', as referenced in proc(5).
Reference(s):
. 12/2018, item origins added (and commit msg history)
commit 96d59cbf46
. 01/2019, <stat> origins tweaked
commit 201e816b26
Signed-off-by: Jim Warner <james.warner@comcast.net>
Rather than offer three separate patches, they've been
consolidated in this single commit. All are related in
that they surfaced while preparing a subsequent patch.
------------------------------------------------------
library: correct a broken '#if define', <SLABINFO> api
It was introduced (embarrassingly) in the patch below.
Reference(s):
commit 97d078a9af
------------------------------------------------------
library: correct a broken 'GET' macro, <DISKSTATS> api
In the patch referenced below, which purported to make
all the 'GET' macros robust, the 'DISKSTATS_GET' macro
was broken. A necessary parameter wasn't passed to the
subsequently invoked function: procps_diskstats_get().
Reference(s):
commit bef8c7fb70
------------------------------------------------------
library: correct a broken 'sort' func, <DISKSTATS> api
In the commit shown below, an attempt to normalize the
errno handling, the sort function inadvertently lost 1
crucial line of code which produces a consistent SEGV.
Reference(s):
commit 06be33b43e
Signed-off-by: Jim Warner <james.warner@comcast.net>
Since the patch referenced below traded a compile-time
'sizeof' directive for a run-time 'strlen' call, there
is no need to declare lxc patterns as explicit arrays.
We'll also use the actual lxc patterns by omitting the
beginning slashes ('/') for both of those definitions.
And, looking to the future when most/all lxc users are
using the most recent lxc release, we will make things
slightly more efficient by reversing those two pattern
literals so the most recent pattern was checked first.
Of course, such a change only benefits tasks which are
running in a container. For the majority of processes,
both literals will be compared in that 'if' statement,
assuming the 'LXC' field is currently being displayed.
[ plus, a leftover parenthesis pair has been removed ]
Reference(s):
commit 288d759b8b
Signed-off-by: Jim Warner <james.warner@comcast.net>
This patch just polishes the 'origin' comments for the
<STAT> header file. In particular those derived/unique
items (the 'SUM' guys) will now be properly explained.
[ in order to employ the 'derived from above' phrase ]
[ with their DELTA versions, all SUM items had to be ]
[ relocated (and some renamed). in turn, that had an ]
[ impact on many portions of the .c source file too. ]
Reference(s):
. summary calculations introduced
commit 2c86c4984a
. origins added to header files
commit 96d59cbf46
Signed-off-by: Jim Warner <james.warner@comcast.net>
This small change is an outgrowth of the research into
the bug represented by that merge request shown below.
With the master branch, a real buglet was subsequently
addressed. In this newlib branch, no bug existed since
the <stat> API relies solely on just cpus reflected in
(and parsed from) the kernel's /proc/stat pseudo file.
[ since that procps_stat_new() priming read about to ]
[ be performed will value info->cpus.total, there is ]
[ no need to separately invoke a procps_cpu_count(). ]
Reference(s):
https://gitlab.com/procps-ng/procps/merge_requests/82
Signed-off-by: Jim Warner <james.warner@comcast.net>
The merge request shown below prompted (thankfully) an
examination of our lxc containers logic in readproc.c.
As it turns out, the lxc folks changed that eyecatcher
used to identify containers within a task cgroup file.
So this patch, with little extra cost, will enable the
libprocps lxc_containers() guy to handle both strings.
[ additionally, I was shocked to find lxc allows the ]
[ eyecatcher to be changed at ./configure time. such ]
[ a provision has always existed. unfortunately, the ]
[ changed value was only available to root, assuming ]
[ one wished to tackle that undocumented liblxc api. ]
Reference(s):
. what prompted lxc support reevaluation
https://gitlab.com/procps-ng/procps/merge_requests/82
. original lxc support introduced
commit 0557504f9c
Signed-off-by: Jim Warner <james.warner@comcast.net>
A lack of documentation seems to be the major obstacle
to releasing this new library. So, in an effort to get
the ball rolling again, this patch adds the origins of
each item as a comment to six of the new header files.
However, before reviewing how such changes may benefit
that documentation objective, it seemed appropriate to
first reflect on newlib's background & current status.
___________________________________________ BACKGROUND
Discussions about and work on a new library began back
in July 2012 but quickly died. After a lull of 2 years
those discussions were resumed in August 2014 but soon
died also (and no code survived the gitorious demise).
With those early discussions, the recommended approach
was to encapsulate all of the libprocps data offerings
in individual functions. When it came to extensibility
it was suggested we should rely on symbols versioning.
Unfortunately that approach would have made for a huge
Application Programming Interface virtually impossible
to master or even document. And, runtime call overhead
would have been substantial for ps and especially top.
So, an alternative design was sought but there were no
new suggestions/contributions via freelists or gitlab.
Thus, in spite of a lack of library design experience,
the procps-ng team (Craig & Jim) set out to develop an
alternative API, more concise and with lower overhead.
Reference(s):
. 07/01/2012, begin library design discussion
https://www.freelists.org/post/procps/Old-library-calls
. 08/12/2014, revival of library design discussion
https://www.freelists.org/post/procps/libprocs-redesign
_____________________________________ DESIGN EVOLUTION
Our newlib branch first appeared on June 14, 2015. And
our current API actually represents the 4th generation
during the past 3 years of evolution. First, there was
a basic 'new', 'get' and 'unref' approach, using enums
to minimize the proliferation of 'get' function calls.
Then, in anticipation of other programs like ps, where
multiple fields times multiple processes would greatly
increase the number of 'get' function calls, a concept
of 'chains' was introduced. This became generation #2.
Such 'chains' proved unnecessarily complex so 'stacks'
replaced them. This was considered the 3rd generation,
but too many implementation details were still exposed
requiring those users to 'alloc', 'read', 'fill', etc.
Finally, a 4th generation emerged representing several
refinements to standardize and minimize those exported
functions, thus hiding all implementation details from
the users. Lastly, handling of 'errno' was normalized.
Reference(s):
. 06/14/2015, revival of new API discussion
https://www.freelists.org/post/procps/The-library-API-again
. 06/24/2015, birth of the newlib branch
https://www.freelists.org/post/procps/new-library
. 06/29/2015, 2nd generation introduced 'chains'
https://www.freelists.org/post/procps/new-library,8
. 07/22/2015, 3rd generation introduced 'stacks'
https://www.freelists.org/post/procps/newlib-stacks-vs-chains
. 06/18/2016, 4th generation refinements begin
https://www.freelists.org/post/procps/newlib-generation-35
. 11/10/2017, 4th generation standardized 'errno'
https://www.freelists.org/post/procps/some-more-master-newlib-stuff
_______________________________________ CURRENT DESIGN
Central to this new design is a simple 'result' struct
reflecting an item plus its value (thanks to a union).
As a user option, these item structures can be grouped
into 'stacks', yielding many results with just 1 call.
Such a 'stack' can be seen as a variable length record
whose content/order is determined solely by the users.
Within that 'result' structure, the union has standard
C language types so there is never a doubt how a value
should be used in a printf statement. Given that linux
requires a least a 32-bit platform the only difference
in capacity surrounds 'long' integers. And, where such
types might be used, the 32-bit maximums are adequate.
The items themselves are simply enumerators defined in
the respective header files. A user can name any items
of interest then the library magically provides result
structure(s). The approach was proven to be extensible
without breaking the ABI (in commit referenced below).
The 6 major APIs each provide for the following calls:
. 'new' ---------> always required as the first call .
. 'ref' -------------------------> strictly optional .
. 'unref' --------> optional, if ill-behaved program .
. 'get' --------------------> retrieve a single item .
. 'select' ----------------> retrieve multiple items .
And the 'get' and 'select' functions provide for delta
results representing the difference between successive
get/select calls (or a 'new' then 'get/select' call).
For the <diskstats>, <pids>, <slabinfo> & <stat> APIs,
where results are unpredictable, a 'reap' function can
return multiple result structures for multiple stacks.
The <pids> API differs from others in that those items
of interest must be provided at 'new' or 'reset' time,
a function unique to this API. And the <pids> 'select'
function requires PIDs or UIDs which are to be fetched
which then operates as a subset of 'reap'. Lastly, the
'get' function is an iterator for successive PIDs/TIDs
returning items previously identified via 'new/reset'.
To provide assistance to users during development, the
special header 'proc/xtra-procps-debug.h' is available
to check type usage against library expectations. That
check is activated by including this header explicitly
or via build using: ./configure '-DXTRA_PROCPS_DEBUG'.
Reference(s):
. 08/05/2016, type validation introduced
https://www.freelists.org/post/procps/newlib-types-validation
commit e3270d463d
. 08/11/2016, extensibility while preserving ABI example
https://www.freelists.org/post/procps/new-meminfo-fields
commit 09e1886c9e
_________________________ INITIAL DOCUMENTATION EFFORT
The initial attempt, referenced below, dealt primarily
with the <pids> interface. Separate man pages for each
exported function were created. Plus there was another
document describing the items, among other miscellany.
Adopting such an approach encounters several problems:
1. In order to use these man pages, users are required
to already know how to use the library. Or alternately
one could randomly search each of them while trying to
ascertain which function call satisfies their need and
what exactly was the proper compliment/order required.
2. While we can explain what all of those <pids> items
represent, that certainly isn't true for all the APIs.
See the gaps in kernel documentation for <meminfo> and
complete lack of documentation with that <vmstat> API.
3. Our documentation effort should take pains to avoid
unnecessary implementation details. Here's an example:
. "The pointer to info will have memory"
. "allocated and a structure created."
Alternatively, the following conveys user requirements
while not offering any internal implementation detail:
. "You must provide the address of a NULL"
. "info structure pointer."
Reference(s):
. 01/04/2017, initial documentation offering
https://www.freelists.org/post/procps/Using-reap-and-get
commit 2598e9f2ce
___________________ RECOMMENDED DOCUMENTATION APPROACH
I recommend that the newlib documentation consist of 3
man pages only. The first would cover the 5 major APIs
and their common functions. The second would deal with
the <pids> API exclusively, explaining how it differs.
Any remaining exported libproc functions which are yet
to be included could be represented in a 3rd document.
For these new documents the following are are assumed:
1. Since we will not be able to document all items, we
shouldn't try to document any items. We should instead
rely on proc(5) or Documentation/filesystems/proc.txt.
2. Program development often involves referencing some
header file(s). So, make that an absolute requirement.
3. With the addition of item origins, represented with
this commit, and considering that 'types' were already
present, the header file might be all some users need.
4. And who knows, when a user of our libproc complains
about gaps in their documentation, it might prompt the
kernel folks to correct those long standing omissions.
To summarize, I suggest that we replace that libproc.3
document with a more general one explaining the basics
of accessing this new library and the common calls for
most of the major interfaces. We can then create a new
document (libproc-pids.3?), which explains differences
in using the <PIDS> application programming interface.
A final document (libproc-misc.3?) covers what's left.
Signed-off-by: Jim Warner <james.warner@comcast.net>
This change is being made in anticipation of adding the
source origin of each item to the <pids.h> header file.
Signed-off-by: Jim Warner <james.warner@comcast.net>
This patch will bring the <meminfo> API into line with
that proc(5) document. There were several undocumented
fields that were not noted and these two were omitted:
. 'MmapCopy' was conditional on the #define CONFIG_MMU
. 'Quicklists' depends on the #define CONFIG_QUICKLIST
And we're about to get the following new field in 4.20
which will be represented, at least, in that proc.txt:
. 'KReclaimable' will include SReclaimable plus others
Signed-off-by: Jim Warner <james.warner@comcast.net>
If we ever were to eliminate the procps.h header file,
as discussed in the thread referenced below, then that
would impair the current XTRA_PROCPS_DEBUG provisions.
The only remaining way to verify result types would be
to explicitly include that <proc/xtra-procps-debug.h>.
So, this commit will once again enable the ./configure
provision for defining the -DXTRA_PROCPS_DEBUG option.
Reference(s):
https://www.freelists.org/post/procps/newlib-Qualys-patches,6
Signed-off-by: Jim Warner <james.warner@comcast.net>
