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Date: Fri, 3 Nov 2006 12:30:01 -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 Fri, 3 Nov 2006, Jens Axboe wrote: > Try to time it (visual output of the app is not very telling, and it's > buffered) and then apply some profiling. OK, a little more info. I added gettimeofday() calls after each call to io_submit(), put the timevals in an array, and after everything was done computed the difference between each timeval and the program start time, as well as the deltas. I got this: 0: 0.080s 1: 0.086s 0.006s 2: 0.102s 0.016s 3: 0.111s 0.008s 4: 0.118s 0.007s 5: 0.134s 0.015s 6: 0.141s 0.006s 7: 0.148s 0.006s 8: 0.158s 0.009s 9: 0.164s 0.006s ... 96: 1.036s 0.007s 97: 1.044s 0.007s 98: 1.147s 0.102s 99: 1.155s 0.008s 98 appears to be an aberration. Perhaps three of the times on an average run are around a tenth of a second; all of the others are pretty steady at 7 or 8 microseconds. So, it's basically linear in its time consumption. Does 7 microseconds seem a bit excessive for an io_submit (and a gettimeofday)? -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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