|Summary:||Poor SSD performance|
|Component:||Serial ATA||Assignee:||Jeff Garzik (jgarzik)|
|Severity:||normal||CC:||akpm, alan, rjw, tj|
|Bug Depends on:|
Kernel 2.6.29 log file
dmesg from booting kernel 2.6.29
18.104.22.168 kernel boot log.
22.214.171.124 kernel boot log.
Description Jake 2009-06-05 17:37:07 UTC
I have experienced a 3-fold performance cut on read times for my OCZ Vertex 30GB SATAII SSD between kernel versions 2.6.28 and 2.6.29. In 2.6.28, hdparm and other tests showed read speeds of 200-220 MB/s on my Vertex drive. In kernel 2.6.29, I perform the same tests and find read speeds of 70-80 MB/s. I did not benchmark the write speeds. Kernel architecture is x86_64. Let me know if there's anything else I should check out. I discussed this in the Arch linux forums here: http://bbs.archlinux.org/viewtopic.php?pid=562748#p562748, but we did not make any progress diagnosing the problem.
Comment 1 Andrew Morton 2009-06-05 17:48:17 UTC
I marked this as a regression.
Comment 2 Tejun Heo 2009-06-07 03:12:26 UTC
Can you please attach boot logs from the two kernels?
Comment 4 Jake 2009-06-07 04:37:13 UTC
Comment on attachment 21781 [details] Kernel 2.6.29 log file This file corresponds to booting kernel 2.6.29 when I get slow SSD reads.
Comment 5 Jake 2009-06-07 04:37:52 UTC
Created attachment 21782 [details] dmesg from booting kernel 2.6.29
Comment 6 Jake 2009-06-07 04:39:08 UTC
I also can submit kernel.log and dmesg from boots of the 126.96.36.199 kernel in which I get full read speeds. I will do this if you think it is necessary.
Comment 7 Tejun Heo 2009-06-07 04:41:29 UTC
Yeap, that was what I meant by "the two kernels". Sorry about not being clear.
Comment 8 Tejun Heo 2009-06-07 04:42:32 UTC
Also, you attached 25 and 20 byte files which only contain the file names.
Comment 10 Jake 2009-06-07 12:22:57 UTC
Created attachment 21786 [details] 188.8.131.52 kernel boot log.
Comment 11 Jake 2009-06-07 12:23:36 UTC
I'm sorry, I should have checked the files before uploading them. The proper files are now uploaded.
Comment 12 Tejun Heo 2009-06-08 02:45:02 UTC
Hmm... can't see any ATA related differences. Can you please run the following command as root in 2.6.28 and 29 and report the results? # dd if=/dev/sda of=/dev/null iflag=direct bs=1M count=1024 Thanks.
Comment 13 Jake 2009-06-08 02:49:32 UTC
In 2.6.28 and 2.6.29 the direct flag gives me 230 MB/s reads.
Comment 14 Tejun Heo 2009-06-08 04:02:41 UTC
In the original report, what 'other tests' showed large performance regression other than hdparm? Also, does hdparm give consistent numbers over multiple trials?
Comment 15 Jake 2009-06-08 04:04:49 UTC
dd if=/dev/sda of=/dev/null also gives me read speeds of 70-80 MB/s in 2.6.29, where I get 220 MB/s in 2.6.28.
Comment 16 Tejun Heo 2009-06-08 04:09:09 UTC
Hmm... I see. The difference is from far above the block/storage layer. Most likely vm. Andrew, can you please take it? Thanks.
Comment 17 Jake 2009-06-16 04:01:25 UTC
I installed a version of the 2.6.30 kernel and this problem appears to be absent since I got read speeds of 220MB/s. Apparently this problem is isolated to the 2.6.29 kernel.
Comment 18 Tejun Heo 2009-06-17 06:24:25 UTC
Heh... so it solved itself. It would be nice to find out which was the culprit. I suppose the right people would already know. Anyways, with 2.6.30 already out of the door, I don't think it's of high priority. Jeff, can you please close this one? Thanks.