On Mon, 28 Jul 2008 13:34:12 +0900 Hisashi Hifumi [off-list ref] wrote:

Hi

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Are there significant numbers of people using block size < page size in
situations where performance is important and significantly improved by
this patch? Can you give any performance numbers to illustrate perhaps?

With XFS lots of people use 4k blocksize filesystems on ia64 systems
with 16k pages, so an optimization like this would be useful.

As Nick says, we really should have some measurement results which
confirm this theory.  Maybe we did do some but they didn't find theor
way into the changelog.

I've put the patch on hold until this confirmation data is available.

I've got some performance number.
I wrote a benchmark program and got result number with this program.
This benchmark do:
	1, mount and open a test file.
	2, create a 512MB file.
	3, close a file and umount.
	4, mount and again open a test file.
	5, pwrite randomly 300000 times on a test file. offset is aligned by IO size(1024bytes).
	6, measure time of preading randomly 100000 times on a test file.

The result was:
	2.6.26
        330 sec

	2.6.26-patched
        226 sec

Arch:i386 
Filesystem:ext3
Blocksize:1024 bytes
Memory: 1GB

On ext3/4, a file is written through buffer/block. So random read/write mixed workloads
or random read after random write workloads are optimized with this patch under 
pagesize != blocksize environment. This test result showed this.

OK, thanks.  Those are pretty nice numbers for what is probably a
fairly common workload.