lkml.org 
[lkml]   [2018]   [Jan]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] mm: numa: Do not trap faults on shared data section pages.
    On Tue, Jan 16, 2018 at 11:28:44AM -0800, Henry Willard wrote:
    > Workloads consisting of a large number processes running the same program
    > with a large shared data section may suffer from excessive numa balancing
    > page migration of the pages in the shared data section. This shows up as
    > high I/O wait time and degraded performance on machines with higher socket
    > or node counts.
    >
    > This patch skips shared copy-on-write pages in change_pte_range() for the
    > numa balancing case.
    >
    > Signed-off-by: Henry Willard <henry.willard@oracle.com>
    > Reviewed-by: Håkon Bugge <haakon.bugge@oracle.com>
    > Reviewed-by: Steve Sistare steven.sistare@oracle.com

    Merge the leader and this mail together. It would have been nice to see
    data on other realistic workloads as well.

    My main source of discomfort is the fact that this is permanent as two
    processes perfectly isolated but with a suitably shared COW mapping
    will never migrate the data. A potential improvement to get the reported
    bandwidth up in the test program would be to skip the rest of the VMA if
    page_mapcount != 1 in a COW mapping as it would be reasonable to assume
    the remaining pages in the VMA are also affected and the scan is wasteful.
    There are counter-examples to this but I suspect that the full VMA being
    shared is the common case. Whether you do that or not;

    Acked-by: Mel Gorman <mgorman@suse.de>

    --
    Mel Gorman
    SUSE Labs

    \
     
     \ /
      Last update: 2018-01-16 22:26    [W:2.116 / U:0.012 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site