On Wed, Oct 2, 2013 at 11:22 AM, Xianghua Xiao <xiaoxianghua@xxxxxxxxx> wrote: > This is indeed a 40G user case. Thanks for the info on > default_cmdsn_depth, it's set to 16 on 3.8.x kernel and I am changing > it to 64. > > How can I enable MCS and/or I_T nexus? At the moment I want to see how > fast the stack can handle iSCSI/RAID5 throughput. > > Thanks, > xiao > > > On Tue, Oct 1, 2013 at 4:16 PM, Nicholas A. Bellinger > <nab@xxxxxxxxxxxxxxx> wrote: >> On Wed, 2013-10-02 at 01:14 +0800, Xianghua Xiao wrote: >>> I used lio-utils to get iscsi working, however during testing I found >>> out that only 2 out of 12 cores are being used by LIO-TARGET(iblock), >>> why is that? >>> >>> Used SCST in the past and the workload was shared by all the cores by >>> default, so it's a surprise to me with LIO-iscsi that it picks one >>> core for Tx and one core for Rx, the rest cores are sitting idle? >>> >>> any help is appreciated. >>> >> >> Two items here. >> >> First, you'll want to bump the per TPG attribute value for >> default_cmdsn_depth from the default 16 to something larger (64 or 128). >> >> This value controls how many outstanding commands the initiator is >> allowed to dispatch on a per session basis, and increasing the value >> allows a larger pipe (10 Gb/sec for example) to keep more active >> commands in flight. The default value has also been increased to a >> higher value starting in v3.12-rc1 code in the patch here: >> >> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/target/iscsi?id=38f7d6edbf91693bb679bb29901c8296e7838cd9 >> >> Second, in order to scale the number of threads used for I/O submission, >> you'll either want to enable MC/S (multiple connections per session), or >> use multiple sessions (typically across multiple ports) with multipath >> on the client side. >> >> --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
