Hi Vladislav, On Mon, 2013-06-24 at 18:18 +0300, Vladislav Bogdanov wrote: > Hi, > > I'm evaluating performance of different targets (actually LIO and IET) > on top of RAID5 > (mdraid) for my customer. > > In this particular test (streaming write in several threads) load is > provided by a windows 7 > machine with robocopy and its default settings (8 threads). > > As expected, blockio writes are slow for both targets (~33 Mb/s), fileio > with wb cache performs better. > > What is really weird, is that kernel version affects fileio+wb a lot, > but in a different directions > for targets. > > I have similar iscsi parameters for both targets (except 3.4's LIO misses > MaxRecvDataSegmentLength), and I set Wthreads=2 for IET. > > What I see: > > IET (with fileio+wb) shows: > > * 75 MB/s with kernel 3.4 (from debian) > * 85 MB/s with kernel 3.9 > > LIO (with fileio+wb) shows: > > * 63 MB/s with kernel 3.4 (from debian) > * 54 MB/s with kernel 3.9 > > Is there any explanation for LIO performance degradation with the kernel > upgrade? > Strange. Can you verify using a TPG attribute default_cmdsn_depth value larger than the hardcoded default of 16..? IIRC, IET is using a larger CmdSN window by default here, so you'll want to increase default_cmdsn_depth=128 with this type of workload. Also, verifying with a RAMDISK_MCP backend on the same setup would be useful for determining if it's a FILEIO specific performance issue. Thanks for reporting! --nab -- To unsubscribe from this list: send the line "unsubscribe target-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
