Message-ID: <a4aa2e13-7187-600b-c628-7e8fb108def0@intel.com>
Date:   Tue, 28 Feb 2023 08:32:31 +0800
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Subject: Re: [linus:master] [mm] f1a7941243: unixbench.score -19.2% regression
To:     Shakeel Butt <shakeelb@google.com>
CC:     "willy@infradead.org" <willy@infradead.org>,
        "tj@kernel.org" <tj@kernel.org>,
        "dennis@kernel.org" <dennis@kernel.org>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        lkp <lkp@intel.com>,
        "zhengjun.xing@linux.intel.com" <zhengjun.xing@linux.intel.com>,
        "Huang, Ying" <ying.huang@intel.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "Tang, Feng" <feng.tang@intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "m.szyprowski@samsung.com" <m.szyprowski@samsung.com>,
        "Sang, Oliver" <oliver.sang@intel.com>,
        "linux-trace-kernel@vger.kernel.org" 
        <linux-trace-kernel@vger.kernel.org>,
        "oe-lkp@lists.linux.dev" <oe-lkp@lists.linux.dev>
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From:   "Yin, Fengwei" <fengwei.yin@intel.com>
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Hi Shakeel,

On 2/28/2023 12:50 AM, Shakeel Butt wrote:
> On Sun, Feb 26, 2023 at 10:35 PM Yin, Fengwei <fengwei.yin@intel.com> wrote:
>>
>> Hi Andrew, Shakeel,
>>
>> On Tue, 2023-01-31 at 10:26 -0800, Shakeel Butt wrote:
>>> +per-cpu memory maintainers for FYI.
>>>
>>> Thread started at
>>> https://lore.kernel.org/linux-mm/202301301057.e55dad5b-oliver.sang@intel.com/
>>>
>>> On Mon, Jan 30, 2023 at 9:57 PM Shakeel Butt <shakeelb@google.com>
>>> wrote:
>>>>
>>> [...]
>>>>>
>>>>> We could cut down the number of calls to pcpu_alloc() by a factor
>>>>> of 4
>>>>> by having a pcpu_alloc_bulk() that would allocate all four RSS
>>>>> counters
>>>>> at once.
>>>>>
>>>>> Just throwing out ideas ...
>>>>
>>>> Thanks, I will take a stab at pcpu_alloc_bulk() and will share the
>>>> result tomorrow.
>>>>
>>>
>>> OK, not a one day effort.
>>>
>>> Andrew, which option do you prefer?
>>>
>>> 1. Keep the patches as the test workload (fork ping pong) is not a
>>> representative of real world workload and work on improving
>>> pcpu_alloc() for 6.4+.
>>>
>>> 2. Revert the patches for now, improve pcpu_alloc() and re-introduce
>>> the patches once we confirm that fork-ping-pong is not regressed
>>> anymore.
>> This performance regression still can be reproduced on latest master
>> branch. So we took option1 here. Right? Thanks.
>>
> 
> Yes unless some real workload reports regression.
Thanks for the confirmation.

Regards
Yin, Fengwei

> 
> Shakeel