lkml.org 
[lkml]   [2020]   [May]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 1/2] sched/uclamp: Add a new sysctl to control RT default boost value
    On 05/29/20 11:21, Mel Gorman wrote:
    > On Thu, May 28, 2020 at 05:51:31PM +0100, Qais Yousef wrote:
    > > > Indeed, that one. The fact that regular distros cannot enable this
    > > > feature due to performance overhead is unfortunate. It means there is a
    > > > lot less potential for this stuff.
    > >
    > > I had a humble try to catch the overhead but wasn't successful. The observation
    > > wasn't missed by us too then.
    > >
    >
    > As with all things, it's perfectly possible I was looking at a workload
    > where the cost is more obvious but given that the functions are inlined,
    > it's not trivial to spot. I just happened to spot it because I was paying
    > close attention to try_to_wake_up() at the time.

    Indeed.

    >
    > > On my Ubuntu 18.04 machine uclamp is enabled by default by the way. 5.3 kernel
    > > though, so uclamp task group stuff not there yet. Should check how their server
    > > distro looks like.
    > >
    >
    > Elsewhere in the thread, I showed some results based on 5.7 so uclamp
    > task group existed but I had it disabled. The uclamp related parts of
    > the kconfig were
    >
    > # zgrep UCLAMP kconfig-5.7.0-rc7-with-clamp.txt.gz
    > CONFIG_UCLAMP_TASK=y
    > CONFIG_UCLAMP_BUCKETS_COUNT=5
    > # CONFIG_UCLAMP_TASK_GROUP is not set

    So you never had the TASK_GROUP part enabled when you noticed the regression?
    Or is it the other way around, you just disabled CONFIG_UCLAMP_TASK_GROUP to
    'fix' it?

    Thanks

    --
    Qais Yousef

    \
     
     \ /
      Last update: 2020-05-29 17:11    [W:4.162 / U:0.120 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site