lkml.org 
[lkml]   [2015]   [Sep]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] arm64: Increase the max granular size
    Will,

    On 22.09.15 19:29:02, Will Deacon wrote:
    > On Tue, Sep 22, 2015 at 06:59:48PM +0100, Robert Richter wrote:
    > > From: Tirumalesh Chalamarla <tchalamarla@cavium.com>
    > >
    > > Increase the standard cacheline size to avoid having locks in the same
    > > cacheline.
    > >
    > > Cavium's ThunderX core implements cache lines of 128 byte size. With
    > > current granulare size of 64 bytes (L1_CACHE_SHIFT=6) two locks could
    > > share the same cache line leading a performance degradation.
    > > Increasing the size fixes that.
    >
    > Do you have an example of that happening?

    I did some 'poor man's kernel build all modules benchmarking' and
    could not find significant performance improvements so far (second
    part with the patch reverted):

    build-allmodules-4.2.0-01404-g5818d6e89783.log:real 7m10.490s
    build-allmodules-4.2.0-01404-g5818d6e89783.log:real 6m59.747s
    build-allmodules-4.2.0-01404-g5818d6e89783.log:real 6m59.264s
    build-allmodules-4.2.0-01404-g5818d6e89783.log:real 7m0.435s
    build-allmodules-4.2.0-01404-g5818d6e89783.log:real 6m59.569s
    build-allmodules-4.2.0-01404-g5818d6e89783.log:real 6m59.274s
    build-allmodules-4.2.0-01404-g5818d6e89783.log:real 7m0.507s
    build-allmodules-4.2.0-01404-g5818d6e89783.log:real 7m1.551s
    build-allmodules-4.2.0-01404-g5818d6e89783.log:real 6m59.073s
    build-allmodules-4.2.0-01404-g5818d6e89783.log:real 7m1.738s

    build-allmodules-4.2.0-01406-g638c69fddc40.log:real 7m10.644s
    build-allmodules-4.2.0-01406-g638c69fddc40.log:real 6m59.814s
    build-allmodules-4.2.0-01406-g638c69fddc40.log:real 7m0.315s
    build-allmodules-4.2.0-01406-g638c69fddc40.log:real 6m59.610s
    build-allmodules-4.2.0-01406-g638c69fddc40.log:real 6m59.885s
    build-allmodules-4.2.0-01406-g638c69fddc40.log:real 6m59.281s
    build-allmodules-4.2.0-01406-g638c69fddc40.log:real 7m0.869s
    build-allmodules-4.2.0-01406-g638c69fddc40.log:real 7m0.953s
    build-allmodules-4.2.0-01406-g638c69fddc40.log:real 7m0.787s
    build-allmodules-4.2.0-01406-g638c69fddc40.log:real 7m0.656s

    I will check what kind of workloads this patch was written for.
    Tirumalesh, any idea?

    Thanks,

    -Robert

    >
    > > Increasing the size has no negative impact to cache invalidation on
    > > systems with a smaller cache line. There is an impact on memory usage,
    > > but that's not too important for arm64 use cases.
    >
    > Do you have any before/after numbers to show the impact of this change
    > on other supported SoCs?



    \
     
     \ /
      Last update: 2015-09-25 17:21    [W:2.516 / U:0.508 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site