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From: Vladislav Bolkhovitin <vst@vlnb.net>
To: Jens Axboe <axboe@kernel.dk>, Sitsofe Wheeler <sitsofe@gmail.com>
Cc: "fio@vger.kernel.org" <fio@vger.kernel.org>
Subject: Re: Fio high IOPS measurement mistake
Date: Thu, 03 Mar 2016 20:37:36 -0800	[thread overview]
Message-ID: <56D91110.8080203@vlnb.net> (raw)
In-Reply-To: <20160303162037.GD22164@kernel.dk>

Jens Axboe wrote on 03/03/2016 08:20 AM:
> On Thu, Mar 03 2016, Sitsofe Wheeler wrote:
>> On 3 March 2016 at 03:03, Vladislav Bolkhovitin <vst@vlnb.net> wrote:
>>> For those who asked about perf profiling, it remained the same as before with the CPU
>>> consumption is all about timekeeping and memset:
>>>
>>> -  55.74%  fio  fio                [.] clock_thread_fn
>>>      clock_thread_fn
>>
>> Perhaps this is what is already included above but could you use the
>> -g option on perf to collect it into a call-graph and post the top
>> results?
> 
> The above looks like a side effect of using gtod_cpu, it'll burn one
> core. For the original poster - did you verify whether using gtod_cpu
> was faster than using the CPU clock source in each CPU?

Yes, I had verified it and mentioned in one of my reports. It slightly decreased the
IOPS. I guess, it's a locking contention somewhere.

Thanks,
Vlad



  reply	other threads:[~2016-03-04  4:37 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-01  5:17 Fio high IOPS measurement mistake Vladislav Bolkhovitin
2016-03-01  6:01 ` Sitsofe Wheeler
2016-03-02  4:25   ` Vladislav Bolkhovitin
2016-03-02  7:38     ` Sitsofe Wheeler
2016-03-03  3:02       ` Vladislav Bolkhovitin
2016-03-02 18:37     ` Elliott, Robert (Persistent Memory)
2016-03-03  3:03       ` Vladislav Bolkhovitin
2016-03-03 21:03         ` Elliott, Robert (Persistent Memory)
2016-03-04  4:36           ` Vladislav Bolkhovitin
2016-03-03  3:03     ` Vladislav Bolkhovitin
2016-03-03  7:10       ` Sitsofe Wheeler
2016-03-03  7:13         ` Sitsofe Wheeler
2016-03-04  4:37           ` Vladislav Bolkhovitin
2016-03-03 16:20         ` Jens Axboe
2016-03-04  4:37           ` Vladislav Bolkhovitin [this message]
2016-03-04 15:33             ` Jens Axboe
2016-03-05  0:47               ` Vladislav Bolkhovitin
2016-03-05  0:54                 ` Jens Axboe
2016-03-05  1:09                   ` Vladislav Bolkhovitin
2016-03-04  4:37         ` Vladislav Bolkhovitin
2016-03-02  8:26 ` Andrey Kuzmin
2016-03-03  3:02   ` Vladislav Bolkhovitin

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