We originally approached the potential problem of
% CPU distortions as unique to Nehalem type cpus.
The latest information suggests that it may have
been due to a kernel anomaly that has since been
corrected.
Yet even without such a cpu, wide disparities in
tics allocation among all available cpus have
sometimes been observed -- spikes as it were in
the normal pattern. This has happened under both
version 2.26.38-13 and 3.0.0-15 kernels.
The small amount of additional code addressing the
original problem carries very little overhead. It
is being retained to afford protection against any
future tic accounting aberrations.
In this commit, supporting programmer comments have
been divorced from any particular cpu type. Also,
another variable and manifest constant will now be
eliminated when CPU_ZEROTICS is defined.
References:
commit 02508b3d76http://www.freelists.org/post/procps/CStates-handling-new-switch,50
The calibrate_fields function had grown too large and
was adversly impacting maintainence. So half of the
logic was split out into a new function.
Now, maintainence of column headers and the required
library flags is organized as follows:
. adj_geometry (calibrate_fields helper)
provides low-level support for sigwinch, memory
. build_headers (calibrate_fields helper)
constructs the headers and library flags
. calibrate_fields
establishes which fields will be displayed
( note the alpha order mentioned in a prior commit )
Signed-off-by: Jim Warner <james.warner@comcast.net>
The top program is carefully organized into sections
and those sections are carefully placed so as to avoid
the need for prototypes. *
Additionally, names of functions are carefully chosen
to maintain alphabetical order within each section.
The names of most 'helper' functions, which are always
placed immediately above the calling functions, often
only met the spirit of the alphabetical law, not the
actual letter of that law.
This commit alters the names of such helper functions
so as to mainatin strict ascii alphabetical order
within each section.
* the single exception to prototypes is find_string,
which calls the task_show function, and would have
prompted a massive reorganization.
Signed-off-by: Jim Warner <james.warner@comcast.net>
The recently added logic dealing with "missing" tics
is mutually exclusive with logic associated with a
define called CPU_ZEROTICS.
This commit expands the use of that define to exclude
such Nehalem logic as appropriate.
It also extends programmer notes in top.h to include
an attribution for initiating the topic of potential
Nehalem type % CPU distortions, acknowledging:
Jaromir Capik, <jcapik@redhat.com>
References
commit ce1410a51a
commit 9e7dd43ab7
commit a9041a5526
Due to a poorly constructed temporary fprintf
used during development, an earlier commit went
a little too far in its computations. The net
result was the code looked nice but actually
accomplished nothing.
It is the /proc/stat line 1 (summary line)
whose tics must be used in establishing the
threshold boundary. And that calculation
need be performed just once per frame.
This commit ensures one threshold calculation
per delay interval no matter how many cpus
are ultimately displayed.
It also corrects scalability by factoring in
the total number of online processors.
Reference:
commit 9e7dd43ab7
The original approach to potential % CPU distortion due
to Nehalem type cores being turned off completely when
idle worked ok until the user typed something.
At that point, elapsed tics would no longer equal the
calculated value producing an undesirable 100% idle
condition until the next update or <Enter/Space> key.
This commit employs actual elapsed tics in determining
whether a cpu should be considered idle and thus makes
top's individual cpu display immune to user keystrokes.
This patch provides for cpu cores which can be turned
off completely when idle (Nehalem, etc.) thus registering
very few or no tics since the last update cycle.
When CPU_ZEROTICS is not defined (the default), any
displayed cpu with less than a certain amount of total
tics will show as 100% idle. That amount is tempered
by the delay interval and total number of cpus.
This commit also satisfies the Debian 'top_nohz' patch
(11/24/09) in a slightly more efficient manner. That
patch concerned kernels built with CONFIG_NO_HZ.
Reference:
http://www.freelists.org/post/procps/CStates-handling-new-switch,4
Prior to this patch, top was able to handle any hotplugged
cpus *added* to the system in two distinct ways.
1) Newly added cpus would be detected by sysinfo_refresh
calling the library's cpuinfo function, which occurs
at most every 5 minutes.
2) The user could force a refresh using either the
<Enter> or <Space> keys.
Unfortunately, the *loss* of a cpu would produce an early
exit due to a /proc/stat read failure. Such a failure
can be produced in the following way:
sudo echo 0 > /sys/devices/system/cpu/cpu??/online
This commit allows top to tolerate the loss of cpus.
It also provides for more efficient CPU_t management,
especially for massively parallel cpu environments.
Note: Changes to the cpu compliment can produce a single
cycle distortion of cpu percentages. Such distortion is
most visible when each cpu is being displayed. It can
be eliminated with a forced refresh via <Enter>/<Space>.
This commit addresses a long standing buglet (debian #441166) which
surfaces when the display mode is switched between task and threads.
An extra procps refresh is now forced upon such a transition which
parallels the approach used at startup for the exact same reason.
Reference: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=441166
This commit corrects some outdated programmer comments.
Additionally, certain nls justifications might become
increasingly obscure with the passage of time so some
previous nls commit text has been added as comments.
summary of changes:
. adopted relative paths to 'include' and 'proc'
dirs so that stand alone compiles are made
easier and no one need guess their locations
. corrected several names for enums and macro
usage reflecting fmt vs. txt
. expanded all octal escape sequences to a full
3 digits since one already required 3 digits
. finalized translator hints (for now)
programming note:
as an aside, by not including an argument for
the gettext --add-comments, any preceeding c
style comment will be propagated to the .pot
file, if the gettext macro isn't empty.
/* Need Not Say 'TRANSLATORS' ...
snprintf(buf, sizeof(buf), "%s", _( // unseen
/* Translator Hint: ...
snprintf(buf, sizeof(buf), "%s", _("" // seen
