Messages in this thread | | | Date | Mon, 12 Jul 2004 21:07:01 -0700 | From | Andrew Morton <> | Subject | Re: [ck] Re: Preempt Threshold Measurements |
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William Lee Irwin III <wli@holomorphy.com> wrote: > > On Mon, Jul 12, 2004 at 10:48:50PM -0400, Gabriel Devenyi wrote: > > Well I'm not particularly educated in kernel internals yet, here's some > > reports from the system when its running. > > 6ms non-preemptible critical section violated 4 ms preempt threshold starting > > at do_munmap+0xd2/0x140 and ending at do_munmap+0xeb/0x140 > > [<c014007b>] do_munmap+0xeb/0x140 > > [<c01163b0>] dec_preempt_count+0x110/0x120 > > [<c014007b>] do_munmap+0xeb/0x140 > > [<c014010f>] sys_munmap+0x3f/0x60 > > [<c0103ee1>] sysenter_past_esp+0x52/0x71 > > Looks like ZAP_BLOCK_SIZE may be too large for you. Lowering that some > may "help" this. It's probably harmless, but try lowering that to half > of whatever it is now, or maybe 64*PAGE_SIZE. It may be worthwhile > to restructure how the preemption points are done in unmap_vmas() so > we don't end up in some kind of tuning nightmare.
Does that instrumentation patch have the cond_resched_lock() fixups? If not, this is a false positive.
The current setting of ZAP_BLOCK_SIZE is good for sub-500usec latencies on a recentish CPU.
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