From: Jesse Barnes <jsbarnes@google.com>
To: Salman Qazi <sqazi@google.com>
Cc: "Theodore Y. Ts'o" <tytso@mit.edu>, Jens Axboe <axboe@kernel.dk>,
Ming Lei <ming.lei@redhat.com>,
Bart Van Assche <bvanassche@acm.org>,
Christoph Hellwig <hch@lst.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-block@vger.kernel.org, Gwendal Grignou <gwendal@google.com>
Subject: Re: BLKSECDISCARD ioctl and hung tasks
Date: Wed, 12 Feb 2020 17:24:19 -0800 [thread overview]
Message-ID: <CAJmaN=kYvGWs=e_ee-DgRs2yW1UFgypKGxOTW2u1MSz1zkmHgQ@mail.gmail.com> (raw)
In-Reply-To: <CAKUOC8UwjUyX1Ou-Gad29-DsyYHMtmLjwV9_0ghGUx=ys_drbA@mail.gmail.com>
On Wed, Feb 12, 2020 at 5:20 PM Salman Qazi <sqazi@google.com> wrote:
>
> On Wed, Feb 12, 2020 at 3:07 PM Theodore Y. Ts'o <tytso@mit.edu> wrote:
> >
> > This is a problem we've been strugging with in other contexts. For
> > example, if you have the hung task timer set to 2 minutes, and the
> > system to panic if the hung task timer exceeds that, and an NFS server
> > which the client is writing to crashes, and it takes longer for the
> > NFS server to come back, that might be a situation where we might want
> > to exempt the hung task warning from panic'ing the system. On the
> > other hand, if the process is failing to schedule for other reasons,
> > maybe we would still want the hung task timeout to go off.
> >
> > So I've been meditating over whether the right answer is to just
> > globally configure the hung task timer to something like 5 or 10
> > minutes (which would require no kernel changes, yay?), or have some
> > way of telling the hung task timeout logic that it shouldn't apply, or
> > should have a different timeout, when we're waiting for I/O to
> > complete.
>
> The problem that I anticipate in our space is that a generous timeout
> will make impatient people reboot their chromebooks, losing us
> information
> about hangs. But, this can be worked around by having multiple
> different timeouts. For instance, a thread that is expecting to do
> something slow, can set a flag
> to indicate that it wishes to be held against the more generous
> criteria. This is something I am tempted to do on older kernels where
> we might not feel
> comfortable backporting io_uring.
I was going to reply along the same lines when I got distracted by a
mtg. If anything I'd like to see a LOWER hung task timeout, generally
speaking. And maybe that means having more operations be asynchronous
like Ted suggests (I'm generally a fan of that anyway).
[snipped good suggestion about async interface]
Jesse
next prev parent reply other threads:[~2020-02-13 1:24 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 [this message]
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
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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