[Cluster-devel] [GFS2 PATCH] GFS2: Average in only non-zero round-trip times for congestion stats
Steven Whitehouse
swhiteho at redhat.com
Thu Apr 23 17:59:16 UTC 2015
Hi,
On 23/04/15 17:45, Bob Peterson wrote:
> ----- 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 <rpeterso at redhat.com>
> 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
That looks very encouraging I think, definitely a good step forward.
Acked-by: Steven Whitehouse <swhiteho at redhat.com>
Steve.
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