Messages in this thread |  | | Date | Thu, 2 Nov 2000 14:59:12 -0700 | From | Val Henson <> | Subject | Re: [BUG] /proc/<pid>/stat access stalls badly for swapping process, 2.4.0-test10 |
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On Thu, Nov 02, 2000 at 08:19:06AM +0100, Mike Galbraith wrote: > On Wed, 1 Nov 2000, Rik van Riel wrote: > > > I have one possible reason for this .... > > > > 1) the procfs process does (in fs/proc/array.c::proc_pid_stat) > > down(&mm->mmap_sem); > > > > 2) but, in order to do that, it has to wait until the process > > it is trying to stat has /finished/ its page fault, and is > > not into its next one ... > > > > 3) combine this with the elevator starvation stuff (ask Jens > > Axboe for blk-7 to alleviate this issue) and you have a > > scenario where processes using /proc/<pid>/stat have the > > possibility to block on multiple processes that are in the > > process of handling a page fault (but are being starved) > > I'm experimenting with blk.[67] in test10 right now. The stalls > are not helped at all. It doesn't seem to become request bound > (haven't instrumented that yet to be sure) but the stalls persist. > > -Mike
This is not an elevator starvation problem.
I also experienced these stalls with my IDE-only system. Unless I'm badly mistaken, the elevator is only used on SCSI disks, therefore elevator starvation cannot be blamed for this problem. These stalls are particularly annoying since I want to find the pid of the process hogging memory in order to kill it, but the read from /proc stalls for 45 seconds or more.
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