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From: Bart Van Assche <bvanassche@acm.org>
To: Salman Qazi <sqazi@google.com>
Cc: Ming Lei <ming.lei@redhat.com>, Jens Axboe <axboe@kernel.dk>,
	Christoph Hellwig <hch@lst.de>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-block@vger.kernel.org, Gwendal Grignou <gwendal@google.com>,
	Jesse Barnes <jsbarnes@google.com>
Subject: Re: BLKSECDISCARD ioctl and hung tasks
Date: Thu, 13 Feb 2020 21:49:47 -0800	[thread overview]
Message-ID: <de7b841c-a195-1b1e-eb60-02cbd6ba4e0a@acm.org> (raw)
In-Reply-To: <CAKUOC8U1H8qJ+95pcF-fjeu9hag3P3Wm6XiOh26uXOkvpNngZg@mail.gmail.com>

On 2020-02-13 11:21, Salman Qazi wrote:
> AFAICT, This is not actually sufficient, because the issuer of the bio
> is waiting for the entire bio, regardless of how it is split later.
> But, also there isn't a good mapping between the size of the secure
> discard and how long it will take.  If given the geometry of a flash
> device, it is not hard to construct a scenario where a relatively
> small secure discard (few thousand sectors) will take a very long time
> (multiple seconds).
> 
> Having said that, I don't like neutering the hung task timer either.

Hi Salman,

How about modifying the block layer such that completions of bio
fragments are considered as task activity? I think that bio splitting is
rare enough for such a change not to affect performance of the hot path.

How about setting max_discard_segments such that a discard always
completes in less than half the hung task timeout? This may make
discards a bit slower for one particular block driver but I think that's
better than hung task complaints.

Thanks,

Bart.

  parent reply	other threads:[~2020-02-14  5:49 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-12 22:27 BLKSECDISCARD ioctl and hung tasks Salman Qazi
2020-02-12 23:06 ` Theodore Y. Ts'o
2020-02-13  1:20   ` Salman Qazi
2020-02-13  1:24     ` Jesse Barnes
2020-02-13  8:26 ` Ming Lei
2020-02-13 17:48   ` Bart Van Assche
2020-02-13 19:21     ` Salman Qazi
2020-02-13 22:08       ` Salman Qazi
2020-02-14  0:25       ` Ming Lei
2020-02-14  5:49       ` Bart Van Assche [this message]
2020-02-14  9:22         ` Ming Lei
2020-02-14 19:42           ` Salman Qazi
2020-02-15  3:46             ` Ming Lei
2020-02-18 16:11               ` Jesse Barnes
2020-02-19  1:37                 ` Ming Lei
2020-02-19  2:54                 ` Ming Lei
2020-02-19 17:54                   ` Salman Qazi
2020-02-19 22:22                     ` Ming Lei
2020-02-19 22:26                       ` Salman Qazi

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