From: Kuan-Wei Chiu <visitorckw@gmail.com>
To: Richard Weinberger <richard@nod.at>
Cc: Christoph Hellwig <hch@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
chengzhihao1 <chengzhihao1@huawei.com>,
jserv <jserv@ccns.ncku.edu.tw>, eleanor15x <eleanor15x@gmail.com>,
marscheng <marscheng@google.com>,
linux-mtd <linux-mtd@lists.infradead.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] lib/list_sort: introduce list_sort_nonatomic() and clean up scheduling workarounds
Date: Thu, 19 Mar 2026 13:37:14 +0800 [thread overview]
Message-ID: <abuLijcND3mqnUoa@google.com> (raw)
In-Reply-To: <566555015.53186.1773828471518.JavaMail.zimbra@nod.at>
On Wed, Mar 18, 2026 at 11:07:51AM +0100, Richard Weinberger wrote:
> ----- Ursprüngliche Mail -----
> > Von: "Christoph Hellwig" <hch@infradead.org>
> >> This change leaves the generic list_sort() completely free of
> >> scheduling hacks, simplifies UBIFS's callbacks, and ensures that legacy
> >> long-list sorting workloads remain safe from soft lockups on
> >> non-preemptible kernels.
> >
> > As said before we really should not add the extra nonatomic API
> > and just do the right thing, and drop the cond_resched in ubifs
> > in a prep patch.
>
> I think you are right. After inspecting UBIFS's usage of list_sort()
> I feel more confident that we can remove the calls to cond_resched()
> from the compare functions.
>
> The compare functions are rather cheap, they don't do (blocking)
> MTD io.
> In the GC case each list contains at most as many UBIFS nodes you can
> stuff into a single LEB.
> The replay case is a little different, the replay list can contain
> elements from multiple LEBs. But the UBIFS journal is limited to
> a few LEBs, so the list is likely always at most a few thousand
> elements long.
> So, we always talk about calling the compare functions a few thousand
> times, not millions times.
>
Great, thanks for verifying this.
I'll prepare a v3 to drop the cond_resched() calls from UBIFS's cmp(),
and remove the if(!++count) from list_sort().
Regards,
Kuan-Wei
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prev parent reply other threads:[~2026-03-19 5:37 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-17 16:59 [PATCH v2] lib/list_sort: introduce list_sort_nonatomic() and clean up scheduling workarounds Kuan-Wei Chiu
2026-03-18 5:57 ` Christoph Hellwig
2026-03-18 10:07 ` Richard Weinberger
2026-03-19 5:37 ` Kuan-Wei Chiu [this message]
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