linux-kernel - Re: [PATCH REPOST blktests v2 7/9] nvme-rc: Calculate IO size for fio jobs

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Message-ID: <7qew4jvwfgvpsqlci6dh6r6vjmzrzaphbqzzxqvvpdfadkj3ab@vxvbvh26bvji>
Date:   Fri, 21 Apr 2023 09:03:33 +0200
From:   Daniel Wagner <dwagner@...e.de>
To:     Hannes Reinecke <hare@...e.de>
Cc:     linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org, Chaitanya Kulkarni <kch@...dia.com>,
        Shin'ichiro Kawasaki <shinichiro@...tmail.com>
Subject: Re: [PATCH REPOST blktests v2 7/9] nvme-rc: Calculate IO size for
 fio jobs

On Fri, Apr 21, 2023 at 08:33:46AM +0200, Hannes Reinecke wrote:
 > +_nvme_calc_rand_io_size() {
> > +	local img_size_mb
> > +	local io_size_mb
> > +
> > +	img_size_mb="$(convert_to_mb "$1")"
> > +	io_size_mb="$(printf "%d" $((((img_size_mb * 1024 * 1024) / $(nproc) - 1) / 1024)))"
> > +
> 
> ... ending with ridiculous small io sizes on machines with lots of CPUs.
> Please cap nproc by something sane like 32.

Yeah, propably not really good long time strategy. I was wondering if we should
make run_fio() variants smarter and do the size callculation there and not by
the callee. If we do this, we could make the number of jobs dependend on CPUs
and image size a bit nicer.