On Sat, 2011-03-05 at 12:46 -0500, 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. > > 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? > The background thread performs the conversion when IOs from async dio writing to holes/preallocated is completed. So would need to setup fallocated files and running async and direct IO would possible to exercise any potential scalability issue with the background dio conversion thread... I took a look at FFSB, it doesn't support fallocate and async IO yet. But fio does support aio and fallocate. This is a simple fio profile I use for test file being setup by fallocate() and run random aio dio over it. See it is useful for Eric to give it a try or a reference on his 48 core. examples$ cat aio-setup ; Random read/write to fallocat files with aio dio [global] ioengine=libaio direct=1 rw=randrw bs=4k size=2m filesize=1024m fallocate=1 directory=/tmp [file1] iodepth=4 > 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. > > - Ted > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
