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Date: Mon, 6 Nov 2006 01:42:32 -0500 (EST) From: Brent Baccala <cosine@...esoft.org> To: Jens Axboe <jens.axboe@...cle.com> cc: linux-kernel@...r.kernel.org Subject: Re: async I/O seems to be blocking on 2.6.15 On Sun, 5 Nov 2006, Jens Axboe wrote: > On Fri, Nov 03 2006, Brent Baccala wrote: >> >> Does 7 microseconds seem a bit excessive for an io_submit (and a >> gettimeofday)? > > I guess you mean miliseconds, not microseconds. 7 miliseconds seems way > too long. I repeated your test here, and the 100 submits take 97000 > microseconds here - or 97 miliseconds. So that's a little less than 1 > msec per io_submit. Still pretty big. You can experiment with oprofile > to profile where the kernel spends its time in that period. > > -- > Jens Axboe > Yes, of course, milliseconds. I have enough other problems with this program (measured in minutes, and no mistake that) that I doubt I'll be profiling the kernel any time soon, but thank you for your help. More than anything else, you've made me understand that I can't just fire off a bunch of async requests like I'm tossing peanuts across the table. I've really got to pay attention to what's in that kernel queue and how it gets managed. -bwb Brent Baccala cosine@...esoft.org - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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