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Subject: Re: [LKP] [drm/mgag200] 90f479ae51: vm-scalability.median -18.8%
 regression
To:     Thomas Zimmermann <tzimmermann@suse.de>,
        Feng Tang <feng.tang@intel.com>
Cc:     Stephen Rothwell <sfr@canb.auug.org.au>, michel@daenzer.net,
        lkp@01.org, linux-kernel@vger.kernel.org,
        dri-devel <dri-devel@lists.freedesktop.org>
References: <14fdaaed-51c8-b270-b46b-cba7b5c4ba52@suse.de>
 <20190805070200.GA91650@shbuild999.sh.intel.com>
 <c0c3f387-dc93-3146-788c-23258b28a015@intel.com>
 <045a23ab-78f7-f363-4a2e-bf24a7a2f79e@suse.de>
 <37ae41e4-455d-c18d-5c93-7df854abfef9@intel.com>
 <370747ca-4dc9-917b-096c-891dcc2aedf0@suse.de>
 <c6e220fe-230c-265c-f2fc-b0948d1cb898@intel.com>
 <20190812072545.GA63191@shbuild999.sh.intel.com>
 <20190813093616.GA65475@shbuild999.sh.intel.com>
 <64d41701-55a4-e526-17ae-8936de4bc1ef@suse.de>
 <20190824051605.GA63850@shbuild999.sh.intel.com>
 <1b897bfe-fd40-3ae3-d867-424d1fc08c44@suse.de>
 <d114b0b6-6b64-406e-6c3f-a8b8d5502413@intel.com>
 <44029e80-ba00-8246-dec0-fda122d53f5e@suse.de>
From:   Rong Chen <rong.a.chen@intel.com>
Message-ID: <90e78ce8-d46a-5154-c324-a05aa1743c98@intel.com>
Date:   Wed, 28 Aug 2019 17:37:01 +0800
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Hi Thomas,

On 8/28/19 1:16 AM, Thomas Zimmermann wrote:
> Hi
>
> Am 27.08.19 um 14:33 schrieb Chen, Rong A:
>> Both patches have little impact on the performance from our side.
> Thanks for testing. Too bad they doesn't solve the issue.
>
> There's another patch attached. Could you please tests this as well?
> Thanks a lot!
>
> The patch comes from Daniel Vetter after discussing the problem on IRC.
> The idea of the patch is that the old mgag200 code might display much
> less frames that the generic code, because mgag200 only prints from
> non-atomic context. If we simulate this with the generic code, we should
> see roughly the original performance.
>
>

It's cool, the patch "usecansleep.patch" can fix the issue.

commit:
   f1f8555dfb9 drm/bochs: Use shadow buffer for bochs framebuffer console
   90f479ae51a drm/mgag200: Replace struct mga_fbdev with generic 
framebuffer emulation
   b976b04c2bc only schedule worker from non-atomic context

f1f8555dfb9a70a2  90f479ae51afa45efab97afdde b976b04c2bcf33148d6c7bc1a2  
testcase/testparams/testbox
----------------  -------------------------- --------------------------  
---------------------------
          %stddev      change         %stddev      change %stddev
              \          |                \          | \
      42912             -15%      36517 44093 
vm-scalability/performance-300s-8T-anon-cow-seq-hugetlb/lkp-knm01
      42912             -15%      36517 44093        GEO-MEAN 
vm-scalability.median

Best Regards,
Rong Chen