From: Sitsofe Wheeler <sitsofe@gmail.com>
To: "Elliott, Robert (Persistent Memory)" <elliott@hpe.com>
Cc: efortin@cyberspicace.com, fio <fio@vger.kernel.org>,
Jens Axboe <axboe@kernel.dk>
Subject: Re: FIO 3.11
Date: Thu, 18 Oct 2018 05:19:18 +0100 [thread overview]
Message-ID: <CALjAwxg5bDB80+_g2aUvPuTEAsqS=xsP0Htxur=5Zyot8-4UEw@mail.gmail.com> (raw)
In-Reply-To: <AT5PR8401MB1169925565E8213E9968F891ABFF0@AT5PR8401MB1169.NAMPRD84.PROD.OUTLOOK.COM>
On Wed, 17 Oct 2018 at 22:45, Elliott, Robert (Persistent Memory)
<elliott@hpe.com> wrote:
>
>
> These will make each thread implement your desired mix:
>
> rwmixread=int
[...]
> rwmixwrite=int
[...]
> percentage_random=int[,int][,int]
[...]
Another (but more overlooked) option for forcing different jobs into
lockstep with each other is the flow parameter -
https://fio.readthedocs.io/en/latest/fio_doc.html#cmdoption-arg-flow
but it tends to be easiest to reason about when there are just two
jobs.
>
> Threads running sequential accesses can easily benefit from cache hits from each other, if
> there is any caching or prefetching done by the involved drivers or devices. One thread
> takes the lead and suffers delays, while the others benefit from its work and stay close
> behind. They can take turns, but tend to stay clustered together. This can distort results.
> Random accesses avoid that problem, provided the capacity is much larger than any caches.
--
Sitsofe | http://sucs.org/~sits/
next prev parent reply other threads:[~2018-10-18 4:19 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <BN7PR08MB409869032E10FEC58C9CBE08D9FF0@BN7PR08MB4098.namprd08.prod.outlook.com>
2018-10-17 19:03 ` Fwd: FIO 3.11 Jens Axboe
2018-10-17 21:41 ` Elliott, Robert (Persistent Memory)
2018-10-18 0:42 ` Etienne-Hugues Fortin
2018-10-18 4:19 ` Sitsofe Wheeler [this message]
2018-10-18 10:26 ` Etienne-Hugues Fortin
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