Messages in this thread | | | Subject | Re: [RESEND] shm: shm exit scalability fixes | From | Davidlohr Bueso <> | Date | Tue, 17 Jun 2014 10:48:32 -0700 |
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On Tue, 2014-06-17 at 12:27 -0500, Jack Miller wrote: > [ RESEND note: Adding relevant CCs, fixed a couple of typos in commit message, > patches unchanged. Original intro follows. ] > > All - > > This is small set of patches our team has had kicking around for a few versions > internally that fixes tasks getting hung on shm_exit when there are many > threads hammering it at once. > > Anton wrote a simple test to cause the issue: > > http://ozlabs.org/~anton/junkcode/bust_shm_exit.c
I'm actually in the process of adding shm microbenchmarks to perf-bench so I might steal this :-)
> > Before applying this patchset, this test code will cause either hanging > tracebacks or pthread out of memory errors.
Are you seeing this issue in any real world setups? While the program does stress the path you mention quite well, I fear it is very unrealistic... how many shared mem segments do real applications actually use/create for scaling issues to appear?
I normally wouldn't mind optimizing synthetic cases like this, but a quick look at patch 1/3 shows that we're adding an extra overhead (16 bytes) in the task_struct.
In any case, I will take a closer look at the set.
Thanks, Davidlohr
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