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SubjectRe: Performance of ext4
On Mon, 16 Jun 2008, Aneesh Kumar K.V wrote:

> On Mon, Jun 16, 2008 at 07:54:08PM +0200, Jan Kara wrote:
>>> On Thu, 12 Jun 2008, Holger Kiehl wrote:
>>>
>>>> On Thu, 12 Jun 2008, Aneesh Kumar K.V wrote:
>>>>
>>>>> On Thu, Jun 12, 2008 at 02:07:30PM +0000, Holger Kiehl wrote:
>>>>>> This time there is no OOPS and system is still up running without any
>>>>>> problem (except any process wanting to write something to this filesystem
>>>>>> gets stuck forever).
>>>>>>
>>>>>> What can I do to help find the problem? The system is still up with all
>>>>>> those
>>>>>> process hanging in D-state.
>>>>>>
>>>>>
>>>>> if you can login to the system get the dmesg output after
>>>>>
>>>>> echo t > /proc/sysrq-trigger
>>>>>
>>>> Unfortunately I have not set CONFIG_MAGIC_SYSRQ. Tomorrow I will try to
>>>> reproduce this with a kernel that has CONFIG_MAGIC_SYSRQ set.
>>>>
>>> After recompiling, rebooting and run afdbench first I got an OOPS and the
>>> system hanged up solid. The only thing I was able to catch is this:
>>>
>>> RIP [<ffffffff803019f9>] jbd2_journal_release_jbd_inode+0xcb/0x100
>>> RSP <ffff8101fe259c18>
>>>
>>> This was copied by hand. And this I cut 'cut and past' from my terminal:
>>>
>>> kernel: Code: c3 e8 31 ce f3 ff 41 fe 04 24 e8 fe 3f 16 00 4c 89 fe 48 89
>>> df e8 5f cd f3 ff eb 82 48 83 7d 00 00 74 27 48 8b 55 10 48 8b 45 18 <48>
>>> 89 42 08 48 89 10 48 c7 45 18 00 02 20 00 48 c7 45 10 00 01
>> Aneesh found cause of this oops I think... Aneesh, would you send the
>> fix to Holger? Thanks.
>>
>
> That fix was mainly done with the help of Holger. Many thanks to him for
> doing multiple test during weekend with different combination. He had
> already confirmed that the fix worked for me.
>
> There is another issue that he is hitting when running the test with
> mke2fs -m 0. But I think that is not related to lock inversion.
>
Doing several test with '-m 0' I was unable to reproduce this and I could
now do several runs with afdbench. However the results do show that with
ext4-patch-queue it actually slower:

For ext3: 5449.76 files per second 15.58 MiB/s
For ext4: 5162.16 files per second 15.48 MiB/s
For ext4+patch-queue: 4963.6975 files per second 14.73 MiB/s

On the positive side the bonnie++ numbers got much better:

Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
ext3 16G 51501 97 210601 91 100479 32 55528 98 301589 44 1198 5
16G 52702 98 215540 94 99339 32 55376 97 300933 44 1159 4
16G 52426 99 212584 94 99091 31 55656 98 301669 44 1160 4
ext4 16G 52965 98 224199 89 108440 32 56389 99 303792 42 1526 4
16G 52792 98 223980 92 107685 32 56350 98 303066 42 1532 4
16G 52994 98 222354 92 107802 32 56386 99 303727 41 1455 4
ext4(patchqueue)16G 59727 98 252733 52 110177 25 55821 98 296739 42 1553 5
16G 61047 99 239242 48 111664 25 55706 98 297151 42 1545 4
16G 60503 99 241532 47 109655 25 55671 98 297648 42 1552 3

ext3 and ext4 tests where done with 2.6.25.4 and those with patch-queue was
2.6.26-rc5. I will do another test run with 2.6.26-rc5 without patch-queue
just to make sure that the slowdown does not happen due to changes in the
2.6.26 branch.

Another important observation is that ext4+patch-queue does still have the
same error I reported 2 years ago, see:
http://marc.info/?l=linux-ext4&m=115192918624449&w=2

During afdbench the results are written to $HOME/results, see the following
listing before running afdbench:

afdbench@helena:~/results$ ls -ltr
total 260
-rw-r--r-- 1 afdbench afdbench 1274 2008-05-26 09:40 results.10740.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1320 2008-05-26 09:47 results.15132.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1593 2008-05-26 10:03 results.20899.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1499 2008-05-26 10:20 results.30577.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1319 2008-05-26 10:33 results.9819.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1273 2008-05-26 10:40 results.16657.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1274 2008-05-26 10:48 results.21319.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1274 2008-05-26 10:59 results.25168.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1274 2008-05-26 11:05 results.29113.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1274 2008-05-26 11:15 results.1626.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1273 2008-05-26 11:47 results.6247.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1273 2008-05-26 11:53 results.10889.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1274 2008-05-26 12:09 results.8970.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 838 2008-05-26 12:22 results.2635.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1281 2008-05-26 12:35 results.2686.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1327 2008-05-26 12:43 results.7525.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1693 2008-05-26 12:56 results.13665.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1600 2008-05-26 13:15 results.23610.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1600 2008-05-26 15:10 results.13041.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1604 2008-05-26 15:23 results.22862.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1604 2008-05-26 15:43 results.32516.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 14582 2008-05-28 17:16 results.2585.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 14583 2008-05-28 20:17 results.32490.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 14628 2008-05-28 23:19 results.11812.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 14845 2008-05-29 02:22 results.31472.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 21134 2008-05-29 05:30 results.27636.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 21970 2008-05-29 08:40 results.25944.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 3309 2008-05-29 11:11 results.14789.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 3310 2008-05-29 11:43 results.20842.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 4107 2008-06-16 21:45 results.2190.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 4108 2008-06-16 23:04 results.8794.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 4108 2008-06-17 00:22 results.27273.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 4109 2008-06-17 01:41 results.4505.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 8450 2008-06-17 03:05 results.19995.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 9230 2008-06-17 04:35 results.24033.helena.dwd.de

And here is the listing after running the benchmark:

afdbench@helena:~/results$ ls -ltr
total 284
-rw-r--r-- 1 afdbench afdbench 1274 2008-05-26 09:40 results.10740.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1320 2008-05-26 09:47 results.15132.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1593 2008-05-26 10:03 results.20899.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1499 2008-05-26 10:20 results.30577.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1319 2008-05-26 10:33 results.9819.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1273 2008-05-26 10:40 results.16657.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1274 2008-05-26 10:48 results.21319.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1274 2008-05-26 10:59 results.25168.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1274 2008-05-26 11:05 results.29113.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1274 2008-05-26 11:15 results.1626.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1273 2008-05-26 11:47 results.6247.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1273 2008-05-26 11:53 results.10889.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1274 2008-05-26 12:09 results.8970.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 838 2008-05-26 12:22 results.2635.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1281 2008-05-26 12:35 results.2686.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1327 2008-05-26 12:43 results.7525.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1693 2008-05-26 12:56 results.13665.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1600 2008-05-26 13:15 results.23610.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1600 2008-05-26 15:10 results.13041.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1604 2008-05-26 15:23 results.22862.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 1604 2008-05-26 15:43 results.32516.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 14582 2008-05-28 17:16 results.2585.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 14583 2008-05-28 20:17 results.32490.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 14628 2008-05-28 23:19 results.11812.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 14845 2008-05-29 02:22 results.31472.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 21134 2008-05-29 05:30 results.27636.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 21970 2008-05-29 08:40 results.25944.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 3309 2008-05-29 11:11 results.14789.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 3310 2008-05-29 11:43 results.20842.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 4107 2008-06-16 21:45 results.2190.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 4108 2008-06-16 23:04 results.8794.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 4108 2008-06-17 00:22 results.27273.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 4109 2008-06-17 01:41 results.4505.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 8450 2008-06-17 03:05 results.19995.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 8208 2008-06-17 04:35 results.24033.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 8361 2008-06-17 08:19 results.9628.helena.dwd.de
-rw-r--r-- 1 afdbench afdbench 8858 2008-06-17 09:49 results.8134.helena.dwd.de

Note how the size of file results.24033.helena.dwd.de changes from 9230 before
the test to 8208 bytes after the test. Also note the date both have the same
timestamp "2008-06-17 04:35". I have made a copy of results.24033.helena.dwd.de
before the test and compared it with that after the test. The file is just
truncated by 1022 bytes and there is no garbage.

This is reproducible but not always, sometimes only a small part gets truncated
and sometimes several kilobytes get truncated.

Holger



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