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top: protect against the anomalous 'Mem' graph display

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Until this patch, top falsely assumed that there would
always be some (small) amount of physical memory after
subtracting 'used' and 'available' from the total. But
as the issue referenced below attests, a sum of 'used'
and 'available' might exceed that total memory amount.

I'm not sure if this is a problem with our calculation
of the 'used' amount, a flaw in the kernel 'available'
algorithms or some other reason I cannot even imagine.

Anyway, this patch protects against such a contingency
through the following single line addition of new code
. if (pct_used + pct_misc > 100.0 || pct_misc < 0) ...

The check for less than zero is not actually necessary
as long as the source numbers remain unsigned. However
should they ever become signed, we'll have protection.

[ Most of the changes in this commit simply separate ]
[ a variable's definition from its associated logic. ]

Reference(s):
https://gitlab.com/procps-ng/procps/issues/64

Signed-off-by: Jim Warner <james.warner@comcast.net>
This commit is contained in:
Jim Warner 2017-08-17 01:11:11 -05:00 committed by Craig Small
parent e3c729adfa
commit a2ceb95e2a
2 changed files with 13 additions and 7 deletions
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NEWS
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@ -20,6 +20,7 @@ procps-ng-NEXT
* top: fix argument parsing quirk resulting in SEGV Redhat #1450429
* top: delay interval accepts non-locale radix point Redhat #1182248
* top: address a wishlist man page NLS suggestion Debian #865689
* top: fix potential distortion in 'Mem' graph display issue #64
* watch: define HOST_NAME_MAX where not defined Debian #830734
procps-ng-3.3.12

15
top/top.c
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@ -5249,21 +5249,26 @@ numa_nope:
{ "%-.*s~4", "%-.*s~6", "%-.*s~6", Graph_blks }
};
char used[SMLBUFSIZ], util[SMLBUFSIZ], dual[MEDBUFSIZ];
int ix = w->rc.graph_mems - 1;
float pct_used = (float)kb_main_used * (100.0 / (float)kb_main_total),
float pct_used, pct_misc, pct_swap;
int ix, num_used, num_misc;
pct_used = (float)kb_main_used * (100.0 / (float)kb_main_total);
#ifdef MEMGRAPH_OLD
pct_misc = (float)(kb_main_buffers + kb_main_cached) * (100.0 / (float)kb_main_total),
pct_misc = (float)(kb_main_buffers + kb_main_cached) * (100.0 / (float)kb_main_total);
#else
pct_misc = (float)(kb_main_total - kb_main_available - kb_main_used) * (100.0 / (float)kb_main_total),
pct_misc = (float)(kb_main_total - kb_main_available - kb_main_used) * (100.0 / (float)kb_main_total);
#endif
if (pct_used + pct_misc > 100.0 || pct_misc < 0) pct_misc = 0;
pct_swap = kb_swap_total ? (float)kb_swap_used * (100.0 / (float)kb_swap_total) : 0;
ix = w->rc.graph_mems - 1;
#ifndef QUICK_GRAPHS
int num_used = (int)((pct_used * Graph_adj) + .5),
num_used = (int)((pct_used * Graph_adj) + .5),
num_misc = (int)((pct_misc * Graph_adj) + .5);
if (num_used + num_misc > Graph_len) num_misc = Graph_len - num_used;
snprintf(used, sizeof(used), gtab[ix].used, num_used, gtab[ix].type);
snprintf(util, sizeof(util), gtab[ix].misc, num_misc, gtab[ix].type);
#else
(void)num_used; (void)num_misc;
snprintf(used, sizeof(used), gtab[ix].used, (int)((pct_used * Graph_adj) + .5), gtab[ix].type);
snprintf(util, sizeof(util), gtab[ix].misc, (int)((pct_misc * Graph_adj) + .4), gtab[ix].type);
#endif