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Message-ID: <4A48BBF9.6050408@vlnb.net> Date: Mon, 29 Jun 2009 17:04:57 +0400 From: Vladislav Bolkhovitin <vst@...b.net> To: Wu Fengguang <fengguang.wu@...el.com>, Ronald Moesbergen <intercommit@...il.com> CC: Andrew Morton <akpm@...ux-foundation.org>, "kosaki.motohiro@...fujitsu.com" <kosaki.motohiro@...fujitsu.com>, "Alan.Brunelle@...com" <Alan.Brunelle@...com>, "hifumi.hisashi@....ntt.co.jp" <hifumi.hisashi@....ntt.co.jp>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>, "jens.axboe@...cle.com" <jens.axboe@...cle.com>, "randy.dunlap@...cle.com" <randy.dunlap@...cle.com>, Bart Van Assche <bart.vanassche@...il.com> Subject: Re: [RESEND] [PATCH] readahead:add blk_run_backing_dev Wu Fengguang, on 06/29/2009 04:54 PM wrote: > On Mon, Jun 29, 2009 at 06:55:40PM +0800, Vladislav Bolkhovitin wrote: >> Ronald Moesbergen, on 06/29/2009 02:26 PM wrote: >>> 2009/6/29 Wu Fengguang <fengguang.wu@...el.com>: >>>> On Sat, Jun 20, 2009 at 08:29:31PM +0800, Vladislav Bolkhovitin wrote: >>>>> Wu Fengguang, on 06/20/2009 07:55 AM wrote: >>>>>> On Fri, Jun 19, 2009 at 03:04:36AM +0800, Andrew Morton wrote: >>>>>>> On Sun, 7 Jun 2009 06:45:38 +0800 >>>>>>> Wu Fengguang <fengguang.wu@...el.com> wrote: >>>>>>> >>>>>>>>>> Do you have a place where the raw blktrace data can be retrieved for >>>>>>>>>> more in-depth analysis? >>>>>>>>> I think your comment is really adequate. In another thread, Wu Fengguang pointed >>>>>>>>> out the same issue. >>>>>>>>> I and Wu also wait his analysis. >>>>>>>> And do it with a large readahead size :) >>>>>>>> >>>>>>>> Alan, this was my analysis: >>>>>>>> >>>>>>>> : Hifumi, can you help retest with some large readahead size? >>>>>>>> : >>>>>>>> : Your readahead size (128K) is smaller than your max_sectors_kb (256K), >>>>>>>> : so two readahead IO requests get merged into one real IO, that means >>>>>>>> : half of the readahead requests are delayed. >>>>>>>> >>>>>>>> ie. two readahead requests get merged and complete together, thus the effective >>>>>>>> IO size is doubled but at the same time it becomes completely synchronous IO. >>>>>>>> >>>>>>>> : >>>>>>>> : The IO completion size goes down from 512 to 256 sectors: >>>>>>>> : >>>>>>>> : before patch: >>>>>>>> : 8,0 3 177955 50.050313976 0 C R 8724991 + 512 [0] >>>>>>>> : 8,0 3 177966 50.053380250 0 C R 8725503 + 512 [0] >>>>>>>> : 8,0 3 177977 50.056970395 0 C R 8726015 + 512 [0] >>>>>>>> : 8,0 3 177988 50.060326743 0 C R 8726527 + 512 [0] >>>>>>>> : 8,0 3 177999 50.063922341 0 C R 8727039 + 512 [0] >>>>>>>> : >>>>>>>> : after patch: >>>>>>>> : 8,0 3 257297 50.000760847 0 C R 9480703 + 256 [0] >>>>>>>> : 8,0 3 257306 50.003034240 0 C R 9480959 + 256 [0] >>>>>>>> : 8,0 3 257307 50.003076338 0 C R 9481215 + 256 [0] >>>>>>>> : 8,0 3 257323 50.004774693 0 C R 9481471 + 256 [0] >>>>>>>> : 8,0 3 257332 50.006865854 0 C R 9481727 + 256 [0] >>>>>>>> >>>>>>> I haven't sent readahead-add-blk_run_backing_dev.patch in to Linus yet >>>>>>> and it's looking like 2.6.32 material, if ever. >>>>>>> >>>>>>> If it turns out to be wonderful, we could always ask the -stable >>>>>>> maintainers to put it in 2.6.x.y I guess. >>>>>> Agreed. The expected (and interesting) test on a properly configured >>>>>> HW RAID has not happened yet, hence the theory remains unsupported. >>>>> Hmm, do you see anything improper in the Ronald's setup (see >>>>> http://sourceforge.net/mailarchive/forum.php?thread_name=a0272b440906030714g67eabc5k8f847fb1e538cc62%40mail.gmail.com&forum_name=scst-devel)? >>>>> It is HW RAID based. >>>> No. Ronald's HW RAID performance is reasonably good. I meant Hifumi's >>>> RAID performance is too bad and may be improved by increasing the >>>> readahead size, hehe. >>>> >>>>> As I already wrote, we can ask Ronald to perform any needed tests. >>>> Thanks! Ronald's test results are: >>>> >>>> 231 MB/s HW RAID >>>> 69.6 MB/s HW RAID + SCST >>>> 89.7 MB/s HW RAID + SCST + this patch >>>> >>>> So this patch seem to help SCST, but again it would be better to >>>> improve the SCST throughput first - it is now quite sub-optimal. >>>> (Sorry for the long delay: currently I have not got an idea on >>>> how to measure such timing issues.) >>>> >>>> And if Ronald could provide the HW RAID performance with this patch, >>>> then we can confirm if this patch really makes a difference for RAID. >>> I just tested raw HW RAID throughput with the patch applied, same >>> readahead setting (512KB), and it doesn't look promising: >>> >>> ./blockdev-perftest -d -r /dev/cciss/c0d0 >>> blocksize W W W R R R >>> 67108864 -1 -1 -1 5.59686 5.4098 5.45396 >>> 33554432 -1 -1 -1 6.18616 6.13232 5.96124 >>> 16777216 -1 -1 -1 7.6757 7.32139 7.4966 >>> 8388608 -1 -1 -1 8.82793 9.02057 9.01055 >>> 4194304 -1 -1 -1 12.2289 12.6804 12.19 >>> 2097152 -1 -1 -1 13.3012 13.706 14.7542 >>> 1048576 -1 -1 -1 11.7577 12.3609 11.9507 >>> 524288 -1 -1 -1 12.4112 12.2383 11.9105 >>> 262144 -1 -1 -1 7.30687 7.4417 7.38246 >>> 131072 -1 -1 -1 7.95752 7.95053 8.60796 >>> 65536 -1 -1 -1 10.1282 10.1286 10.1956 >>> 32768 -1 -1 -1 9.91857 9.98597 10.8421 >>> 16384 -1 -1 -1 10.8267 10.8899 10.8718 >>> 8192 -1 -1 -1 12.0345 12.5275 12.005 >>> 4096 -1 -1 -1 15.1537 15.0771 15.1753 >>> 2048 -1 -1 -1 25.432 24.8985 25.4303 >>> 1024 -1 -1 -1 45.2674 45.2707 45.3504 >>> 512 -1 -1 -1 87.9405 88.5047 87.4726 >>> >>> It dropped down to 189 MB/s. :( >> Ronald, >> >> Can you, please, rerun this test locally on the target with the latest >> version of blockdev-perftest, which produces much more readable results, > > Is blockdev-perftest public available? It's not obvious from google search. > >> for the following 6 cases: >> >> 1. Default vanilla 2.6.29 kernel, default parameters, including read-ahead > > Why not 2.6.30? :) We started with 2.6.29, so why not complete with it (to save additional Ronald's effort to move on 2.6.30)? >> 2. Default vanilla 2.6.29 kernel, 512 KB read-ahead, the rest is default > > How about 2MB RAID readahead size? That transforms into about 512KB > per-disk readahead size. OK. Ronald, can you 4 more test cases, please: 7. Default vanilla 2.6.29 kernel, 2MB read-ahead, the rest is default 8. Default vanilla 2.6.29 kernel, 2MB read-ahead, 64 KB max_sectors_kb, the rest is default 9. Patched by the Fengguang's patch vanilla 2.6.29 kernel, 2MB read-ahead, the rest is default 10. Patched by the Fengguang's patch vanilla 2.6.29 kernel, 2MB read-ahead, 64 KB max_sectors_kb, the rest is default >> 3. Default vanilla 2.6.29 kernel, 512 KB read-ahead, 64 KB >> max_sectors_kb, the rest is default >> >> 4. Patched by the Fengguang's patch http://lkml.org/lkml/2009/5/21/319 >> vanilla 2.6.29 kernel, default parameters, including read-ahead >> >> 5. Patched by the Fengguang's patch vanilla 2.6.29 kernel, 512 KB >> read-ahead, the rest is default >> >> 6. Patched by the Fengguang's patch vanilla 2.6.29 kernel, 512 KB >> read-ahead, 64 KB max_sectors_kb, the rest is default > > Thanks, > Fengguang > > -- 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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