On 03/05/2011 12:46 PM, Ted Ts'o wrote:
On Thu, Mar 03, 2011 at 11:29:54AM -0800, Mingming Cao wrote:
While running ext4 testing on multiple core, we found there are per
cpu ext4-dio-unwritten threads processing conversion from unwritten
extents to written for IOs completed from async direct IO patch.
Per filesystem is enough, we don't need per cpu threads to work on
conversion.
Signed-off-by: Mingming Cao<cmm@xxxxxxxxxx>
Eric, would you be able to do a very quick sanity check on your
48-core machine? I can definitely see how having a huge number of
threads per file system could be problematic, especially on a system
with 32 or 64 ext4 file systems. I'm curious though if we'll end up
taking a performance hit on direct I/O workloads.
Hi Ted:
Sure, I can do that - I'll queue it up once I'm done with the "for .39"
patch measurements.
If I remember correctly we currently have large file create with DIO
turned off, right? Would it be possible to do a large file create
with DIO enabled, and do a quick run both with and without this patch?
That's right, we're not measuring DIO right now. I think I've got
enough hardware to run a filesystem per core (or more), and I think it
should be straightforward to write a modified ffsb profile to run (say)
48 filesystems in parallel.
In the future it would also be interesting to see how we are doing
versus other file systems using a DIO workload. This is a probably
another area where I suspect some lockstat and oprofile runs may give
us opportunities for further optimization.
Yes - as discussed at Plumber's. I'll put that on the list as well.
With luck, there should be some time towards the end of the .39 merge
window.
Eric
- Ted
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