From: Jeff Moyer <jmoyer@redhat.com>
To: Corrado Zoccolo <czoccolo@gmail.com>
Cc: Linux-Kernel <linux-kernel@vger.kernel.org>,
Jens Axboe <jens.axboe@oracle.com>,
Vivek Goyal <vgoyal@redhat.com>
Subject: Re: [PATCH] cfq-iosched: reduce write depth only if sync was delayed
Date: Fri, 18 Dec 2009 10:32:04 -0500 [thread overview]
Message-ID: <x49iqc42t8r.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <4e5e476b0912110915u209b8923m359d9147cc229fea@mail.gmail.com> (Corrado Zoccolo's message of "Fri, 11 Dec 2009 18:15:20 +0100")
Corrado Zoccolo <czoccolo@gmail.com> writes:
> Hi Jeff,
> On Wed, Dec 9, 2009 at 7:09 PM, Jeff Moyer <jmoyer@redhat.com> wrote:
>> Corrado Zoccolo <czoccolo@gmail.com> writes:
>>
>>> The numbers look good. Now, there is no penalty in having low_latency
>>> set for sequential writes, and just a small penalty for random ones.
>>> The fact that random reads are faster with low_latency set is interesting.
>>> Is the test is running with your patched tiobench (so that the number
>>> of random operations is comparable with sequential ones)?
>>
>> No, I forgot all about that. The number of random operations defaults
>> to 4000, which is pretty low. I'll re-run the tests with a number
>> comparable to the sequential runs. Sorry about that.
>>
> N.P.
> if you have time, can you also re-run the test changing:
> iosched/fifo_expire_async to 8 ?
> I hope that reducing the expire_async, will make cfq quicker at switching
> between the different threads, allowing more parallelism for seq
> writers on your hw.
> If this is the case, I think I can try to estimate the
> fifo_expire_async in the autotuning patch.
Sorry this took so long. I've been rather busy of late.
Cheers,
Jeff
low_latency=1, fifo_expire_async=8
Unit information
================
File size = megabytes
Blk Size = bytes
Rate = megabytes per second
CPU% = percentage of CPU used during the test
Latency = milliseconds
Lat% = percent of requests that took longer than X seconds
CPU Eff = Rate divided by CPU% - throughput per cpu load
Sequential Reads
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.6.32 8192 65536 8 88.39 89.74% 16.388 2032.62 0.00000 0.00000 98
2.6.32 8192 65536 16 90.77 185.3% 32.213 2175.99 0.00000 0.00000 49
Random Reads
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.6.32 8192 65536 8 19.62 25.74% 71.827 3397.26 0.00000 0.00000 76
2.6.32 8192 65536 16 23.82 55.01% 103.361 4075.53 0.00000 0.00000 43
Sequential Writes
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.6.32 8192 65536 8 108.28 1007.% 12.984 5643.55 0.00076 0.00000 11
2.6.32 8192 65536 16 112.40 2014.% 25.430 8592.98 0.00839 0.00000 6
Random Writes
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.6.32 8192 65536 8 63.94 337.7% 22.885 6047.22 0.00076 0.00000 19
2.6.32 8192 65536 16 61.94 662.5% 46.997 12759.69 0.15411 0.00000 9
low_latency=0, fifo_expire_async=8
Unit information
================
File size = megabytes
Blk Size = bytes
Rate = megabytes per second
CPU% = percentage of CPU used during the test
Latency = milliseconds
Lat% = percent of requests that took longer than X seconds
CPU Eff = Rate divided by CPU% - throughput per cpu load
Sequential Reads
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.6.32 8192 65536 8 89.13 88.30% 15.872 3101.39 0.00000 0.00000 101
2.6.32 8192 65536 16 86.78 161.7% 30.794 4909.02 0.00000 0.00000 54
Random Reads
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.6.32 8192 65536 8 20.21 26.64% 69.863 4285.42 0.00000 0.00000 76
2.6.32 8192 65536 16 20.10 52.75% 139.761 5986.94 0.00076 0.00000 38
Sequential Writes
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.6.32 8192 65536 8 108.74 1020.% 13.070 5331.78 0.00076 0.00000 11
2.6.32 8192 65536 16 112.18 2020.% 25.559 7903.16 0.00992 0.00000 6
Random Writes
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.6.32 8192 65536 8 64.53 337.8% 22.671 5388.77 0.00000 0.00000 19
2.6.32 8192 65536 16 61.75 668.9% 47.265 13271.37 0.12894 0.00000 9
next prev parent reply other threads:[~2009-12-18 15:32 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-04 12:35 Corrado Zoccolo
2009-12-05 11:13 ` Corrado Zoccolo
2009-12-06 10:45 ` Corrado Zoccolo
2009-12-06 10:49 ` Jens Axboe
2009-12-07 14:13 ` Jeff Moyer
2009-12-07 14:41 ` Jens Axboe
2009-12-07 16:45 ` Jeff Moyer
2009-12-07 17:04 ` Vivek Goyal
2009-12-07 17:27 ` Vivek Goyal
2009-12-07 18:03 ` Vivek Goyal
2009-12-08 0:07 ` Jeff Moyer
2009-12-08 20:43 ` Corrado Zoccolo
2009-12-09 18:09 ` Jeff Moyer
2009-12-11 17:15 ` Corrado Zoccolo
2009-12-11 17:50 ` Jeff Moyer
2009-12-18 15:32 ` Jeff Moyer [this message]
2009-12-18 21:03 ` Corrado Zoccolo
2009-12-08 18:00 ` Jeff Moyer
2009-12-08 20:46 ` Corrado Zoccolo
2009-12-09 18:16 ` Jeff Moyer
2009-12-09 19:05 ` Jens Axboe
2009-12-09 19:45 Corrado Zoccolo
2009-12-09 19:51 ` Jeff Moyer
2009-12-09 19:54 ` Jens Axboe
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