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    SubjectRe: AMD graphics performance regression in 4.15 and later
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    Hi Jean,

    found the bug reports.

    Here is the original bug report from the kernel:
    https://bugzilla.kernel.org/show_bug.cgi?id=198511

    And here is an fdo bug report where we tried to investigate the root
    cause, but didn't had time for that yet:
    https://bugs.freedesktop.org/show_bug.cgi?id=105038

    Regards,
    Christian.

    Am 06.04.2018 um 10:03 schrieb Christian König:
    > Hi Jean,
    >
    > yeah, that is a known problem. Using huge pages improves the
    > performance because of better TLB usage, but for the cost of higher
    > allocation overhead.
    >
    > What we found is that firefox is doing something rather strange by
    > allocating large textures and then just trowing them away again
    > immediately.
    >
    > We mitigated the problem by avoiding the slow coherent DMA code path
    > on almost all platforms on newer kernels, but essentially somebody
    > needs to figure out why firefox and/or the user space stack is doing
    > this constant allocation/freeing of memory.
    >
    > There is also a bug tracker on bugs.kernel.org about this, but I can't
    > find it any more of hand.
    >
    > Regards,
    > Christian.
    >
    > Am 06.04.2018 um 02:30 schrieb Jean-Marc Valin:
    >> Hi,
    >>
    >> I noticed a serious graphics performance regression between 4.14 and
    >> 4.15. It is most noticeable with Firefox (tried FF57 through FF60) and
    >> causes scrolling to be really choppy/sluggish. I've confirmed that the
    >> problem is also there on 4.16, while 4.13 works fine.
    >>
    >> After a bisection, I've narrowed the regression down to this commit:
    >>
    >> commit 648bc3574716400acc06f99915815f80d9563783
    >> Author: Christian König <christian.koenig@amd.com>
    >> Date:   Thu Jul 6 09:59:43 2017 +0200
    >>
    >>      drm/ttm: add transparent huge page support for DMA allocations v2
    >>
    >>
    >> Some details about my system:
    >> Distro: Fedora 27 (up-to-date)
    >> Video: MSI Radeon RX 560 AERO
    >> CPU: Dual-socket Xeon E5-2640 v4 (20 cores total)
    >> RAM: 128 GB ECC
    >>
    >>
    >> As a comparison, when running Firefox with 4.15 on a Lenovo W540 laptop
    >> (with Intel graphics only) the responsiveness is much better then what
    >> I'm getting on the Xeon machine above with the Radeon card, so this
    >> really seems to be an AMD-only issue.
    >>
    >> Any way to fix the issue?
    >>
    >> Thanks,
    >>
    >>     Jean-Marc
    >> _______________________________________________
    >> dri-devel mailing list
    >> dri-devel@lists.freedesktop.org
    >> https://lists.freedesktop.org/mailman/listinfo/dri-devel
    >

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