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 .