From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bob Peterson Date: Thu, 23 Apr 2015 12:45:01 -0400 (EDT) Subject: [Cluster-devel] [GFS2 PATCH] GFS2: Average in only non-zero round-trip times for congestion stats In-Reply-To: <5538B62C.4030303@redhat.com> References: <1549641874.4770984.1429722009576.JavaMail.zimbra@redhat.com> <5538B62C.4030303@redhat.com> Message-ID: <918499302.5872367.1429807501247.JavaMail.zimbra@redhat.com> List-Id: To: cluster-devel.redhat.com MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit ----- Original Message ----- > Hi, > > That looks better. Do you get better results with it compared with the > previous version? > > Steve. > > On 22/04/15 18:00, Bob Peterson wrote: > > Hi, > > > > This patch changes function gfs2_rgrp_congested so that it only factors > > in non-zero values into its average round trip time. If the round-trip > > time is zero for a particular cpu, that cpu has obviously never dealt > > with bouncing the resource group in question, so factoring in a zero > > value will only skew the numbers. It also fixes a compile error on > > some arches related to division. > > > > Regards, > > > > Bob Peterson > > Signed-off-by: Bob Peterson It's not straightforward because the "preferred rgrps" patch skews the performance results greatly. However, based on my performance tests, yes, the numbers do look better. I temporarily commented out that "preferred rgrps" patch to get a clearer picture. Here are numbers from my testing: This test consists of 5 nodes all simultaneously doing this 'dd' command: dd if=/dev/zero of=/mnt/gfs2/`hostname` bs=1M count=100 (after drop_caches) Stock (nothing disabled): Run 1 -------- pats 716 MB/s jets 615 MB/s bills 669 MB/s dolphins 605 MB/s ravens 735 MB/s -------- Average: 668 MB/s Stock (plus preferred rgrps disabled): AKA 'c3' Run 1 Run 2 -------- -------- pats 766 MB/s 675 MB/s jets 649 MB/s 716 MB/s bills 790 MB/s 735 MB/s dolphins 761 MB/s 727 MB/s ravens 712 MB/s 728 MB/s -------- -------- Average: 736 MB/s 716 MB/s Without latest patch (plus preferred rgrps disabled): AKA 'c2' (In other words, this is the previous patch which was called "GFS2: Use average srttb value in congestion calculations") Run 1 Run 2 Run 3 -------- -------- --------- pats 830 MB/s 688 MB/s 697 MB/s jets 833 MB/s 622 MB/s 645 MB/s bills 831 MB/s 796 MB/s 637 MB/s dolphins 834 MB/s 597 MB/s 690 MB/s ravens 815 MB/s 731 MB/s 734 MB/s -------- -------- --------- Average: 829 MB/s 687 MB/s 681 MB/s Latest patch (plus preferred rgrps disabled): Run 1 Run 2 Run 3 -------- -------- --------- pats 811 MB/s 829 MB/s 652 MB/s jets 825 MB/s 863 MB/s 702 MB/s bills 846 MB/s 825 MB/s 710 MB/s dolphins 845 MB/s 845 MB/s 683 MB/s ravens 820 MB/s 818 MB/s 682 MB/s -------- -------- --------- Average: 829 MB/s 836 MB/s 686 MB/s Latest patch (nothing disabled): Run 1 Run 2 Run 3 -------- -------- --------- pats 834 MB/s 817 MB/s 819 MB/s jets 837 MB/s 835 MB/s 836 MB/s bills 841 MB/s 837 MB/s 834 MB/s dolphins 838 MB/s 851 MB/s 842 MB/s ravens 795 MB/s 808 MB/s 815 MB/s -------- -------- --------- Average: 829 MB/s 830 MB/s 829 MB/s This test (simultaneous dd) is known to be a worst case scenario, so I expect it to show the most improvement. For ordinary block allocations, I don't expect that big of an improvement. Regards, Bob Peterson Red Hat File Systems