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From: Damien Le Moal <Damien.LeMoal@wdc.com>
To: Bart Van Assche <bvanassche@acm.org>,
	Alexander Potapenko <glider@google.com>
Cc: Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>,
	Jens Axboe <axboe@kernel.dk>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	Willem de Bruijn <willemb@google.com>,
	Dmitriy Vyukov <dvyukov@google.com>
Subject: Re: null_handle_cmd() doesn't initialize data when reading
Date: Tue, 12 May 2020 01:42:06 +0000	[thread overview]
Message-ID: <BY5PR04MB690045ED7665BF98A2EA7ED3E7BE0@BY5PR04MB6900.namprd04.prod.outlook.com> (raw)
In-Reply-To: 1e455c9f-4908-f476-f674-c0c920c17f9c@acm.org

On 2020/05/12 10:25, Bart Van Assche wrote:
> On 2020-05-11 16:18, Bart Van Assche wrote:
>> Anyway, can you give the patch below a try?
> 
> The patch in my previous email handles MQ mode but not bio mode. The
> attached patch should handle both.
> 
> Thanks,
> 
> Bart.
> 

Bart,

The patch looks good to me. However, I have one concern regarding the
performance impact of this. When nullblk is used to benchmark the block IO stack
overhead, doing this zeroing unconditionally will likely significantly impact
measured performance. So may be this zeroing feature should be driven by a
modprobe/configfs option ? Doing so, we can keep it off by default, preserving
performance, and turn it on when needed as in Alexander use case.

Thoughts ?

-- 
Damien Le Moal
Western Digital Research

  reply	other threads:[~2020-05-12  1:42 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-15 10:16 null_handle_cmd() doesn't initialize data when reading Alexander Potapenko
2019-11-20 23:12 ` Jens Axboe
2019-11-22 11:58   ` Alexander Potapenko
2019-11-25  4:01     ` Chaitanya Kulkarni
2020-05-10 10:03       ` Alexander Potapenko
2020-05-10 16:20         ` Bart Van Assche
2020-05-11 12:58           ` Alexander Potapenko
2020-05-11 13:01             ` Damien Le Moal
2020-05-11 13:09               ` Alexander Potapenko
2020-05-11 23:18             ` Bart Van Assche
2020-05-12  1:25               ` Bart Van Assche
2020-05-12  1:42                 ` Damien Le Moal [this message]
2020-05-12  2:43                   ` Bart Van Assche
2020-05-12  3:23                     ` Damien Le Moal

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