lkml.org 
[lkml]   [2013]   [Oct]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 17/63] sched: Set the scan rate proportional to the memory usage of the task being scanned
    On 10/07/2013 06:28 AM, Mel Gorman wrote:
    > The NUMA PTE scan rate is controlled with a combination of the
    > numa_balancing_scan_period_min, numa_balancing_scan_period_max and
    > numa_balancing_scan_size. This scan rate is independent of the size
    > of the task and as an aside it is further complicated by the fact that
    > numa_balancing_scan_size controls how many pages are marked pte_numa and
    > not how much virtual memory is scanned.
    >
    > In combination, it is almost impossible to meaningfully tune the min and
    > max scan periods and reasoning about performance is complex when the time
    > to complete a full scan is is partially a function of the tasks memory
    > size. This patch alters the semantic of the min and max tunables to be
    > about tuning the length time it takes to complete a scan of a tasks occupied
    > virtual address space. Conceptually this is a lot easier to understand. There
    > is a "sanity" check to ensure the scan rate is never extremely fast based on
    > the amount of virtual memory that should be scanned in a second. The default
    > of 2.5G seems arbitrary but it is to have the maximum scan rate after the
    > patch roughly match the maximum scan rate before the patch was applied.
    >
    > On a similar note, numa_scan_period is in milliseconds and not
    > jiffies. Properly placed pages slow the scanning rate but adding 10 jiffies
    > to numa_scan_period means that the rate scanning slows depends on HZ which
    > is confusing. Get rid of the jiffies_to_msec conversion and treat it as ms.
    >
    > Signed-off-by: Mel Gorman <mgorman@suse.de>

    Reviewed-by: Rik van Riel <riel@redhat.com>


    --
    All rights reversed


    \
     
     \ /
      Last update: 2013-10-07 20:01    [W:4.060 / U:0.116 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site