From: Matthew Wilcox <willy@infradead.org>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>,
Brian Foster <bfoster@redhat.com>,
linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org
Subject: Re: [PATCH v2 2/2] xfs: kick extra large ioends to completion workqueue
Date: Thu, 6 May 2021 20:45:42 +0100 [thread overview]
Message-ID: <20210506194542.GG388843@casper.infradead.org> (raw)
In-Reply-To: <20210506193406.GE8582@magnolia>
On Thu, May 06, 2021 at 12:34:06PM -0700, Darrick J. Wong wrote:
> On Tue, Oct 06, 2020 at 03:07:20PM +0100, Matthew Wilcox wrote:
> > On Mon, Oct 05, 2020 at 08:55:37PM -0700, Darrick J. Wong wrote:
> > > On Mon, Oct 05, 2020 at 11:21:02AM -0400, Brian Foster wrote:
> > > > We've had reports of soft lockup warnings in the iomap ioend
> > > > completion path due to very large bios and/or bio chains. Divert any
> > > > ioends with 256k or more pages to process to the workqueue so
> > > > completion occurs in non-atomic context and can reschedule to avoid
> > > > soft lockup warnings.
> > >
> > > Hmmmm... is there any way we can just make end_page_writeback faster?
> >
> > There are ways to make it faster. I don't know if they're a "just"
> > solution ...
> >
> > 1. We can use THPs. That will reduce the number of pages being operated
> > on. I hear somebody might have a patch set for that. Incidentally,
> > this patch set will clash with the THP patchset, so one of us is going to
> > have to rebase on the other's work. Not a complaint, just acknowledging
> > that some coordination will be needed for the 5.11 merge window.
>
> How far off is this, anyway? I assume it's in line behind the folio
> series?
Right. The folio series found all kinds of fun places where the
accounting was wrong (eg accounting for an N-page I/O as a single page),
so the THP work is all renamed folio now. The folio patchset I posted
yesterday [1] is _most_ of what is necessary from an XFS point of view.
There's probably another three dozen mm patches to actually enable
multi-page folios after that, and a lot more patches to optimise the
mm/vfs for multi-page folios, but your side of things is almost all
published and reviewable.
[1] https://lore.kernel.org/linux-fsdevel/20210505150628.111735-1-willy@infradead.org/
> > 2. We could create end_writeback_pages(struct pagevec *pvec) which
> > calls a new test_clear_writeback_pages(pvec). That could amortise
> > taking the memcg lock and finding the lruvec and taking the mapping
> > lock -- assuming these pages are sufficiently virtually contiguous.
> > It can definitely amortise all the statistics updates.
>
> /me kinda wonders if THPs arent the better solution for people who want
> to run large ios.
Yes, definitely. It does rather depend on their usage patterns,
but if they're working on a file-contiguous chunk of memory, this
can help a lot.
> > 3. We can make wake_up_page(page, PG_writeback); more efficient. If
> > you can produce this situation on demand, I had a patch for that which
> > languished due to lack of interest.
>
> I can (well, someone can) so I'll talk to you internally about their
> seeekret reproducer.
Fantastic. If it's something that needs to get backported to a
stable-ABI kernel ... this isn't going to be a viable solution.
prev parent reply other threads:[~2021-05-06 19:46 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-02 15:33 [PATCH 0/2] iomap: avoid soft lockup warnings on large ioends Brian Foster
2020-10-02 15:33 ` [PATCH 1/2] iomap: resched ioend completion when in non-atomic context Brian Foster
2020-10-02 15:33 ` [PATCH 2/2] xfs: kick extra large ioends to completion workqueue Brian Foster
2020-10-02 16:19 ` Darrick J. Wong
2020-10-02 16:38 ` Brian Foster
2020-10-03 0:26 ` kernel test robot
2020-10-05 15:21 ` [PATCH v2 " Brian Foster
2020-10-06 3:55 ` Darrick J. Wong
2020-10-06 12:44 ` Brian Foster
2021-05-06 19:31 ` Darrick J. Wong
2021-05-07 14:06 ` Brian Foster
2021-05-07 14:40 ` Matthew Wilcox
2021-05-10 2:45 ` Dave Chinner
2020-10-06 14:07 ` Matthew Wilcox
2021-05-06 19:34 ` Darrick J. Wong
2021-05-06 19:45 ` Matthew Wilcox [this message]
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