Messages in this thread | | | Date | Mon, 16 Aug 2004 12:20:00 -0700 | From | Hans Reiser <> | Subject | Re: [patch] voluntary-preempt-2.6.8.1-P1 |
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Ingo Molnar wrote:
>* Thomas Charbonnel <thomas@undata.org> wrote: > > > >>Tested P1. The biggest offender on my system is still reiserfs' >>search_by_key. The trace is made of a very long loop of : >> 0.016ms (+0.000ms): reiserfs_in_journal (scan_bitmap_block) >> 0.016ms (+0.000ms): find_next_zero_bit (scan_bitmap_block) >>(...) >> 0.977ms (+0.000ms): reiserfs_in_journal (scan_bitmap_block) >> 0.977ms (+0.000ms): find_next_zero_bit (scan_bitmap_block) >>with interrupts showing up in the trace from time to time. Do you have >>plans to fix this, or should I switch to ext3 ? >> >> > >i took a quick look and the reiserfs locking rules in that place do not >seem to be easily fixable - this is the tree-lookup code which i suspect >cannot be preempted. The reiser journalling code also makes use of the >big kernel lock. I'd suggest reporting this to the reiserfs folks > the fix to reiserfs doing single threaded balancing/searching is called reiser4;-) It was not a trivial fix. It is however released.
> and >(if it's not too much effort to migrate) use ext3 meanwhile. > > > >>but the weird thing is that the latency sum goes way above those 100us, >>the culprit being do_IRQ, regularly chewing up to 1ms ! >> >> > > > >> 0.011ms (+0.000ms): enable_8259A_irq (startup_8259A_irq) >> 0.954ms (+0.943ms): do_IRQ (common_interrupt) >> >> > >weird. This has the looks of a preempt-timing bug (we get a timer IRQ >every 1 msec) - but there should be no preempt-timing when we are in the >idle task (swapper). > > > >>http://www.undata.org/~thomas/swapper.trace >> >> > >i'll upload -P2 in a couple of minutes, it will trace the code that >do_IRQ() interrupted too - that would be quite useful in your case. > > Ingo >- >To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >the body of a message to majordomo@vger.kernel.org >More majordomo info at http://vger.kernel.org/majordomo-info.html >Please read the FAQ at http://www.tux.org/lkml/ > > > >
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