Re: [Ext2-devel] [BENCHMARK] fswide dirty bit for ext2

From: Mingming Cao
Date: Thu Mar 30 2006 - 15:16:15 EST


On Tue, 2006-03-28 at 22:57 -0800, Valerie Henson wrote:
> I am working on a file system wide dirty bit for ext2. This allows
> you to skip a full fsck if you crash while the file system is not
> being actively modified.
>
> Zach Brown was kind enough to run a few benchmarks comparing various
> versions of ext2 and ext3. Results:
>
> ext2 ext2r *ext2fw* ext3 ext3wb
> kuntar 17.86 19.59 17.58 21.10 30.60
> postmark 6.41 6.57 8.48 30.87 15.47
> tiobench 34.11 34.96 34.26 34.00 34.06
>
> ext2: ext2: 4k blocks, noatime
> ext2r: ext2: 4k blocks, noatime, reservations
> ext2fw: ext2: 4k blocks, noatime, reservations, fswide
> ext3: ext3: 4k blocks, 256m journal, noatime
> ext3wb: ext3: 4k blocks, 256m journal, noatime, data=writeback
> kuntar: expanding a cached uncompressed kernel tarball and syncing
> postmark: postmark: numbers = 10000, transactions = 10000
> tiobench: tiobench: 16 threads, 256m size
>
> The summary is that ext2+fswide bit is the same as plain ext2 except
> 30% slower on postmark. Slower postmark is expected given the orphan
> inode list requires at least two writes to either the superblock or
> another inode per file removal. An obvious improvement would be
> per-block group orphan inode lists, which would require a non-trivial
> but not frightening patch to fsck. (This might also be ported to
> ext3.) Other ideas?
>
> I split out the ext2 reservations port into its own patch.
> ext2+reservations alone is strangely slower than ext2+fswide on one
> benchmark; I did some preliminary debugging but didn't find anything
> obvious wrong as yet. The patches are available for anyone who wants
> to track this down themselves before I get around to it.
>
Patch looks fine from 5 minutes review. I will look more closely at your
port later. Does this regression on kuntar tests happened on ext3 also?

> Patches against 2.6.16-rc5-mm3 here:
>
> Fswide bit (includes reservations):
>
> http://infohost.nmt.edu/~val/patches/fswide_shorter_patch
>
> Reservations only:
>
> http://infohost.nmt.edu/~val/patches/resv_only_patch
>
> -VAL
>
>
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