Re: [Crash-utility] improve ps performance
----- Original Message -----
Hello Pan,
I've updated the patch I attached yesterday with a change that
caches the most-recent tgid search result. From ~70% to ~90% of
the time, either the last tgid entry or the very next one in the
tgid_array is the one being searched for, so it's not necessary
to call bsearch() every time. "help -t" will show the cache-hit
statistics.
Thanks,
Dave
Hello Pan,
This patch as written needs to be made less restrictive for use
on a live system.
When running on a live system that has many tasks constantly
forking/exec'ing, the "ps" command may occasionally fail like so:
crash> ps
PID PPID CPU TASK ST %MEM VSZ RSS COMM
0 0 0 ffffffff81c13440 RU 0.0 0 0 [swapper/0]
0 0 1 ffff88021282d330 RU 0.0 0 0 [swapper/1]
0 0 2 ffff88021282dac0 RU 0.0 0 0
[swapper/2]
0 0 3 ffff88021282e250 RU 0.0 0 0
[swapper/3]
1 0 1 ffff880212828000 IN 0.0 50140 3120 systemd
2 0 3 ffff880212828790 IN 0.0 0 0 [kthreadd]
... [ cut ] ...
7578 27670 0 ffff8801f45e3c80 DE 0.0 0 0 cc
7622 27668 1 ffff880210ee3c80 ZO 0.0 0 0 info
7629 27667 1 ffff8801075bd330 DE 0.0 0 0 rev
7631 27680 0 ffff8801075bf170 ZO 0.0 0 0 printenv
7635 27685 3 ffff880108bbe9e0 ZO 0.0 0 0 ypwhich
ps: bsearch for tgid failed: task: ffff880210ee6250 tgid: 7654
crash>
Without this patch, the search for the matching tgid would not generate
an error at all, but just quietly continue.
The problem is due to the task.tgid may change on a live system, or more
likely, the task itself may have been re-used.
I would like to fix it simply ignoring tgid bsearch failures on live systems,
and just use the RSS stats stored in the per-tgid mm_struct.
Does that work for you?
Dave