Messages in this thread | | | Date | Tue, 1 Sep 2009 16:14:58 +0800 | From | Wu Fengguang <> | Subject | Re: I/O and pdflush |
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On Mon, Aug 31, 2009 at 10:33:43PM +0800, Fernando Silveira wrote: > On Mon, Aug 31, 2009 at 11:07, Wu Fengguang<fengguang.wu@intel.com> wrote: > > On Mon, Aug 31, 2009 at 10:01:13PM +0800, Wu Fengguang wrote: > >> On Mon, Aug 31, 2009 at 10:00:06PM +0800, Wu Fengguang wrote: > >> > Hi Fernando, > >> > > >> > What's your SSD's IO parameters? Ie. output of this command: > >> > > >> > grep -r . /sys/block/sda/queue/ > >> > > >> > Please replace 'sda' with your SSD device name. > >> > >> Oh I guess it's sdc: > >> > >> grep -r . /sys/block/sdc/queue/ > > Here is it: > > # grep -r . /sys/block/sdc/queue/ > /sys/block/sdc/queue/nr_requests:128 > /sys/block/sdc/queue/read_ahead_kb:128 > /sys/block/sdc/queue/max_hw_sectors_kb:128 > /sys/block/sdc/queue/max_sectors_kb:128 > /sys/block/sdc/queue/scheduler:noop anticipatory [deadline] cfq > /sys/block/sdc/queue/hw_sector_size:512 > /sys/block/sdc/queue/rotational:0 > /sys/block/sdc/queue/nomerges:0 > /sys/block/sdc/queue/rq_affinity:0 > /sys/block/sdc/queue/iostats:1 > /sys/block/sdc/queue/iosched/read_expire:500 > /sys/block/sdc/queue/iosched/write_expire:5000 > /sys/block/sdc/queue/iosched/writes_starved:2 > /sys/block/sdc/queue/iosched/front_merges:1 > /sys/block/sdc/queue/iosched/fifo_batch:16 > # > > These are probably default settings. > > > BTW, would you run "iostat -x 1 5" (which will run 5 seconds) when > > doing I/O in ideal throughput, and when in 25MB/s thoughput state? > > Both files are attached (25mbps = 25MB/s, 80mbps = 80MB/s).
The iostat reported IO size is 64kb, which is half of max_sectors_kb=128. It is strange why the optimal 128kb IO size is not reached in both cases:
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util case 1: sdc 0.00 69088.00 0.00 552.00 0.00 70656.00 128.00 142.75 386.39 1.81 100.10 case 2: sdc 0.00 153504.00 0.00 1200.00 0.00 153600.00 128.00 138.35 115.76 0.83 100.10
Fernando, could you try increasing these deadline parameters by 10 times?
echo 160 > /sys/block/sdc/queue/iosched/fifo_batch echo 50000 > /sys/block/sdc/queue/iosched/write_expire
And try cfq iosched if that still fails? The iostat outputs would be enough during the tests.
Thanks, Fengguang -- 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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