From: Ming Lei <tom.leiming@gmail.com>
To: Bart Van Assche <bvanassche@acm.org>
Cc: Salman Qazi <sqazi@google.com>, 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 <linux-block@vger.kernel.org>,
Gwendal Grignou <gwendal@google.com>,
Jesse Barnes <jsbarnes@google.com>
Subject: Re: BLKSECDISCARD ioctl and hung tasks
Date: Fri, 14 Feb 2020 17:22:57 +0800 [thread overview]
Message-ID: <CACVXFVP114+QBhw1bXqwgKRw_s4tBM_ZkuvjdXEU7nwkbJuH1Q@mail.gmail.com> (raw)
In-Reply-To: <de7b841c-a195-1b1e-eb60-02cbd6ba4e0a@acm.org>
On Fri, Feb 14, 2020 at 1:50 PM Bart Van Assche <bvanassche@acm.org> wrote:
>
> 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.
Are you sure that the task hung warning won't be triggered in case of
non-splitting?
>
> 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.
I am afraid you can't find a golden setting max_discard_segments working
for every drivers. Even it is found, the performance may have been affected.
So just wondering why not take the simple approach used in blk_execute_rq()?
Thanks,
Ming Lei
next prev parent reply other threads:[~2020-02-14 9:23 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
2020-02-14 9:22 ` Ming Lei [this message]
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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