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References: <20190416025934.115252-1-khazhy@google.com> <20190418115326.GE28541@quack2.suse.cz>
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From:   Khazhismel Kumykov <khazhy@google.com>
Date:   Thu, 18 Apr 2019 13:05:56 -0700
Message-ID: <CACGdZYLCi+Or=afmBK8hbP3Ay8x8Oaqnp0Yr+jf1PoQiMc7_DQ@mail.gmail.com>
Subject: Re: [PATCH] ext4: add cond_resched() to ext4_mb_init_backend()
To:     Jan Kara <jack@suse.cz>
Cc:     "Theodore Ts'o" <tytso@mit.edu>, adilger.kernel@dilger.ca,
        linux-ext4@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Thu, Apr 18, 2019 at 4:53 AM Jan Kara <jack@suse.cz> wrote:
>
> On Mon 15-04-19 19:59:34, Khazhismel Kumykov wrote:
> > on non-preempt kernels for filesystems with large number of groups we
> > may take a long time (>50 ticks) initializing all the groups.
> >
> > Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
>
> Thanks for the patch. I'm not opposed to this but I'm just wondering: Has
> this caused any real issues to you? Or how have you come across this
> particular loop? Because I'd think we have more similar loops in ext4
> codebase...
>
>                                                                 Honza
>

We have some instrumentation to warn for these longer periods without
scheduling, which admittedly does trigger relatively frequently from
various places. This particular loop just so happens to be during
system startup where it caught my eye.

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