At Thu, 7 Nov 2013 16:11:17 +0900, FUJITA Tomonori wrote: > > On Wed, 06 Nov 2013 10:04:42 +0900 > Hitoshi Mitake <mitake.hitoshi@xxxxxxxxx> wrote: > > > At Tue, 05 Nov 2013 23:28:45 +0900 (JST), > > FUJITA Tomonori wrote: > > > > > > On Mon, 4 Nov 2013 14:13:16 +0900 > > > Hitoshi Mitake <mitake.hitoshi@xxxxxxxxx> wrote: > > > > > > > From: Hitoshi Mitake <mitake.hitoshi@xxxxxxxxxxxxx> > > > > > > > > Current tgtd sends and receives iSCSI PDUs in its main event > > > > loop. This design can cause bottleneck when many iSCSI clients connect > > > > to single tgtd process. For example, we need multiple tgtd processes > > > > for utilizing fast network like 10 GbE because typical single > > > > processor core isn't fast enough for processing bunch of requests. > > > > > > > > This patch lets tgtd send/receive iSCSI PDUs and check digests in its > > > > worker threads. After applying this patch, the bottleneck in the main > > > > event loop is removed and the performance is improved. > > > > > > > > The improvement can be seen even if tgtd and iSCSI initiator are > > > > running on a single host. Below is a snippet of fio result on my > > > > laptop. The workload is 128MB random RW. Backingstore is sheepdog. > > > > > > > > original tgtd: > > > > read : io=65392KB, bw=4445.2KB/s, iops=1111, runt= 14711msec > > > > write: io=65680KB, bw=4464.8KB/s, iops=1116, runt= 14711msec > > > > > > > > tgtd with this patch: > > > > read : io=65392KB, bw=5098.9KB/s, iops=1274, runt= 12825msec > > > > write: io=65680KB, bw=5121.3KB/s, iops=1280, runt= 12825msec > > > > > > > > This change will be more effective when a number of iSCSI clients > > > > increases. I'd like to hear your comments on this change. > > > > > > > > Signed-off-by: Hitoshi Mitake <mitake.hitoshi@xxxxxxxxxxxxx> > > > > --- > > > > usr/iscsi/iscsi_tcp.c | 291 +++++++++++++++++++++++++++++++++++++++++++++++--- > > > > usr/iscsi/iscsid.c | 61 +++++++---- > > > > usr/iscsi/iscsid.h | 4 + > > > > 3 files changed, 322 insertions(+), 34 deletions(-) > > > > > > This change doesn't affect our complicated logic to handle outstanding > > > commands with tcp disconnection (e.g. conn_close() in conn.c)? > > > > I think it doesn't affect the closing logic. Because any procedure > > other than send/recv and digest checking are not delegated to worker > > threads. Task queuing, connection closing, etc are done in main > > thread even now. > > I've not read the patch but conn_close() has the code to handle a > response to be being sent when a tcp connection is closed. Sorry, the above description is not correct. As you say, some send/recv would be done in the main event loop (e.g. iscsi_free_cmd_task()). But it wouldn't matter because the logic of connection closing is preserved, and connection closing isn't an event which affects performance of tgtd. Thanks, Hitoshi -- To unsubscribe from this list: send the line "unsubscribe stgt" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
