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Message-ID: <465020B8.1010605@gmail.com> Date: Sun, 20 May 2007 12:19:36 +0200 From: Tejun Heo <htejun@...il.com> To: Indan Zupancic <indan@....nu> CC: Jeff Garzik <jeff@...zik.org>, linux-ide@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>, Alan Cox <alan@...rguk.ukuu.org.uk> Subject: Re: [PATCH] sata_sil: Greatly improve DMA support Indan Zupancic wrote: > On Sun, May 20, 2007 00:03, Jeff Garzik wrote: >> Indan Zupancic wrote: >>> This patch seems to work with my SiI 3512, though I don't notice any >>> difference, neither a speedup, nor a slowdown. Hdparm gives the same >>> speeds (-tT), and cp -a'ing kernel sources is abysmal slow in both cases, >>> (need to look into that one) so I didn't really test it that well. >> >> It won't result in much of a speedup, except in situations where IOMMU >> or other situation that causes you to run into the 64k boundary being an >> issue -- generally only on huge transfers. >> >> A good measure is to dd(1) to/from the block device, rather than using a >> filesystem. As has been shown on LKML, the filesystem can really slow >> things down in some cases. > > I didn't really expect a speedup, it's more that I've no regression to report. > > I could benchmark the patch more thoroughly, but right now I'm more worried > about the crawling cp I just discovered. Talking about filesystems slowing down > things... > > Test: > > $ cp -a linux-2.6/ /tmp/ > > done on the same ext3 partition. linux-2.6 contains source and git repo only, > I'm compiling stuff with O=../obj. > > $ vmstat 10 > procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu---- > r b swpd free buff cache si so bi bo in cs us sy id wa > 0 1 0 4168 3316 195700 0 0 739 494 530 393 15 3 66 16 > 0 3 4 4120 2040 198196 0 0 14677 14111 1247 435 0 17 0 83 > 0 1 4 3588 1444 199696 0 0 8892 9472 1362 438 0 12 0 88 > 1 0 4 3772 4228 196012 0 0 764 454 1161 345 0 4 0 96 > 0 1 4 3548 6156 193088 0 0 793 851 1158 340 0 4 0 96 > 0 1 4 3852 7608 189096 0 0 798 523 1160 474 1 4 0 95 > 1 1 4 3612 8684 186048 0 0 1244 864 1178 430 2 5 0 93 > 0 1 4 90660 9308 96396 0 0 853 906 1244 578 7 6 0 87 > 0 1 4 72280 9816 112368 0 0 830 854 1278 429 12 5 0 83 > 1 0 4 52488 10296 130560 0 0 935 861 1178 418 1 6 0 94 > 0 1 4 30500 10788 149776 0 0 977 858 1178 371 0 6 0 94 > 0 1 4 9792 11244 167856 0 0 918 1394 1182 350 1 5 0 94 > 0 1 4 4016 11216 172504 0 0 1017 858 1181 382 1 6 0 94 > 0 1 4 3660 11484 171484 0 0 966 861 1182 410 1 6 0 94 > > It never finished, as I had no patience to copy about 900 Mb with this rate. > > As it's a git tree, I suppose it's heavily fragmented, but this is still rather > pathetic. Should I blame cp, or is something else wrong? Any ideas how > to figure this one out would be appreciated. Sorry for the off-topicness. Do things improve if you change the io scheduler to deadline? # echo deadline > /sys/block/sda/queue/scheduler Also worth looking at is the following bug entry. http://bugzilla.kernel.org/show_bug.cgi?id=7372 There seems to be weird interaction among the scheduler / VM / IO. The exact cause is still not verified. :-( -- tejun - 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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