From: Vincent Fu <vincentfu@gmail.com>
To: Jens Axboe <axboe@kernel.dk>, fio@vger.kernel.org
Cc: Vincent Fu <vincent.fu@samsung.com>
Subject: Re: [PATCH] gettime: fix cpuclock-test on AMD platforms
Date: Tue, 27 Feb 2024 12:38:05 -0500 [thread overview]
Message-ID: <eec27771-3934-42a2-becf-c45501a84e0d@gmail.com> (raw)
In-Reply-To: <dd061da8-a3e0-4824-a650-8db42300af99@kernel.dk>
On 2/27/24 11:34, Jens Axboe wrote:
> On 2/27/24 8:26 AM, Vincent Fu wrote:
>> Starting with gcc 11 __sync_synchronize() compiles to
>>
>> lock or QWORD PTR [rsp], 0
>>
>> on x86_64 platforms. Previously it compiled to an mfence instruction.
>>
>> See line 47 of https://godbolt.org/z/xfE18K7b4 for an example.
>>
>> On Intel platforms this change does not affect the result of fio's CPU
>> clock test. But on AMD platforms, this change causes fio's CPU clock
>> test to fail and fio to fall back to clock_gettime() instead of using
>> the CPU clock for timing.
>>
>> This patch has fio explicitly use an mfence instruction instead of
>> __sync_synchornize() in the CPU clock test code on x86_64 platforms in
>> order to allow the CPU clock test to pass on AMD platforms.
>
> Looks good:
>
> Reviewed-by: Jens Axboe <axboe@kernel.dk>
>
Applied. Thanks.
prev parent reply other threads:[~2024-02-27 17:38 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-27 15:26 [PATCH] gettime: fix cpuclock-test on AMD platforms Vincent Fu
2024-02-27 16:34 ` Jens Axboe
2024-02-27 17:38 ` Vincent Fu [this message]
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