lkml.org 
[lkml]   [2010]   [Jul]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC PATCH] cfq-iosced: Implement IOPS mode and group_idle tunable V3
Vivek Goyal wrote:
> Hi,
>
> This is V3 of the group_idle and CFQ IOPS mode implementation patchset. Since V2
> I have cleaned up the code a bit to clarify the confusion lingering around in
> what cases do we charge time slice and in what cases do we charge number of
> requests.
>
> What's the problem
> ------------------
> On high end storage (I got on HP EVA storage array with 12 SATA disks in
> RAID 5), CFQ's model of dispatching requests from a single queue at a
> time (sequential readers/write sync writers etc), becomes a bottleneck.
> Often we don't drive enough request queue depth to keep all the disks busy
> and suffer a lot in terms of overall throughput.
>
> All these problems primarily originate from two things. Idling on per
> cfq queue and quantum (dispatching limited number of requests from a
> single queue) and till then not allowing dispatch from other queues. Once
> you set the slice_idle=0 and quantum to higher value, most of the CFQ's
> problem on higher end storage disappear.
>
> This problem also becomes visible in IO controller where one creates
> multiple groups and gets the fairness but overall throughput is less. In
> the following table, I am running increasing number of sequential readers
> (1,2,4,8) in 8 groups of weight 100 to 800.
>
> Kernel=2.6.35-rc5-iops+
> GROUPMODE=1 NRGRP=8
> DIR=/mnt/iostestmnt/fio DEV=/dev/dm-4
> Workload=bsr iosched=cfq Filesz=512M bs=4K
> group_isolation=1 slice_idle=8 group_idle=8 quantum=8
> =========================================================================
> AVERAGE[bsr] [bw in KB/s]
> -------
> job Set NR cgrp1 cgrp2 cgrp3 cgrp4 cgrp5 cgrp6 cgrp7 cgrp8 total
> --- --- -- ---------------------------------------------------------------
> bsr 3 1 6186 12752 16568 23068 28608 35785 42322 48409 213701
> bsr 3 2 5396 10902 16959 23471 25099 30643 37168 42820 192461
> bsr 3 4 4655 9463 14042 20537 24074 28499 34679 37895 173847
> bsr 3 8 4418 8783 12625 19015 21933 26354 29830 36290 159249
>
> Notice that overall throughput is just around 160MB/s with 8 sequential reader
> in each group.
>
> With this patch set, I have set slice_idle=0 and re-ran same test.
>
> Kernel=2.6.35-rc5-iops+
> GROUPMODE=1 NRGRP=8
> DIR=/mnt/iostestmnt/fio DEV=/dev/dm-4
> Workload=bsr iosched=cfq Filesz=512M bs=4K
> group_isolation=1 slice_idle=0 group_idle=8 quantum=8
> =========================================================================
> AVERAGE[bsr] [bw in KB/s]
> -------
> job Set NR cgrp1 cgrp2 cgrp3 cgrp4 cgrp5 cgrp6 cgrp7 cgrp8 total
> --- --- -- ---------------------------------------------------------------
> bsr 3 1 6523 12399 18116 24752 30481 36144 42185 48894 219496
> bsr 3 2 10072 20078 29614 38378 46354 52513 58315 64833 320159
> bsr 3 4 11045 22340 33013 44330 52663 58254 63883 70990 356520
> bsr 3 8 12362 25860 37920 47486 61415 47292 45581 70828 348747
>
> Notice how overall throughput has shot upto 348MB/s while retaining the ability
> to do the IO control.
>
> So this is not the default mode. This new tunable group_idle, allows one to
> set slice_idle=0 to disable some of the CFQ features and and use primarily
> group service differentation feature.
>
> If you have thoughts on other ways of solving the problem, I am all ears
> to it.

Hi Vivek

Would you attach your fio job config file?

Thanks
Gui

>
> Thanks
> Vivek
>
>


\
 
 \ /
  Last update: 2010-07-22 09:13    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site