Solofo.Ramangalahy@xxxxxxxx wrote:
On Thu, 16 Oct 2008 07:39:04 -0500, Eric Sandeen <sandeen@xxxxxxxxxx> said:
>> A very thorough test, but the results don't seem to point to a
>> consistent winner.
>>
>> I agree that running without KVM in the picture might be very
>> interesting. Eric has some similar tests underway, I think that
>> his results were also inconclusive so far...
Eric> Yep, I've yet to find an fs_mark invocation, at least, which
Eric> shows a clear winner. I also ran w/ akpm's suggested
Eric> io_schedule watcher patch and never see us waiting on this
Eric> lock (I did set it to 1s though, which is probably too long
Eric> for my storage).
I've redone the tests without kvm. Still no clear winner
To sum up:
. kernel ext4-stable
. mkfs (1.41.3) default options
. mount options: default, akpm, akpm_lock_hack
. scheduler default (cfq)
. 8 cpus, single 15K rpm disk.
. without the high latency detection patch
. a broad range of fs_mark (all the sync strategies, from 1 to 32
threads, up to 10000 files/thread, several directories).
. a "tangled synchrony" workload as mentionned in the "Analysis and
evolution of journaling file systems" paper discussed monday.
First things first, maybe I should have spent more time
reproducing Arjan behavior before testing.
This was not a complete waste of time though, as the following errors
were spotted during the runs:
1. EXT4-fs error (device sdb): ext4_free_inode: bit already cleared for inode 32769
2. EXT4-fs error (device sdb): ext4_init_inode_bitmap: Checksum bad for group 8
3. BUG: spinlock wrong CPU on CPU#3, fs_mark/1975
lock: ffff88015a44f480, .magic: dead4ead, .owner: fs_mark/1975, .owner_cpu: 1
Pid: 1975, comm: fs_mark Not tainted 2.6.27.1-ext4-stable-gcov #1
Call Trace:
[<ffffffff811a47a2>] spin_bug+0xa2/0xaa
[<ffffffff811a481f>] _raw_spin_unlock+0x75/0x8a
[<ffffffff814552c1>] _spin_unlock+0x26/0x2a
[<ffffffffa00d4fd3>] ext4_read_inode_bitmap+0xfa/0x14e [ext4]
[<ffffffffa00d564b>] ext4_new_inode+0x5d4/0xec4 [ext4]
[<ffffffff810562db>] ? __lock_acquire+0x481/0x7d8
[<ffffffffa00c2430>] ? jbd2_journal_start+0xef/0x11a [jbd2]
[<ffffffffa00c2430>] ? jbd2_journal_start+0xef/0x11a [jbd2]
[<ffffffffa00deb99>] ext4_create+0xc7/0x144 [ext4]
[<ffffffff810b6734>] vfs_create+0xdf/0x155
[<ffffffff810b8905>] do_filp_open+0x220/0x7fc
[<ffffffff814552c1>] ? _spin_unlock+0x26/0x2a
[<ffffffff810abe5a>] do_sys_open+0x53/0xd3
[<ffffffff810abf03>] sys_open+0x1b/0x1d
[<ffffffff8100bf8b>] system_call_fastpath+0x16/0x1b
Anybody seen this in their logs?
The "bit already cleared for inode" is triggered by:
fs_mark -v -d /mnt/test-ext4 -n10000 -D10 -N1000 -t8 -s4096 -S0
Arjan,
Do you have any details on the test case that you ran that showed a
clear improvement? What kind of storage & IO pattern did you use?
Regards,
Ric
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