From: Eric Biggers <ebiggers@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-xfs@vger.kernel.org,
William Kucharski <william.kucharski@oracle.com>,
linux-kernel@vger.kernel.org,
linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com,
linux-mm@kvack.org, ocfs2-devel@oss.oracle.com,
linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
linux-erofs@lists.ozlabs.org, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH v9 20/25] ext4: Convert from readpages to readahead
Date: Fri, 20 Mar 2020 11:40:41 -0700 [thread overview]
Message-ID: <20200320184041.GG851@sol.localdomain> (raw)
In-Reply-To: <20200320174848.GC4971@bombadil.infradead.org>
On Fri, Mar 20, 2020 at 10:48:48AM -0700, Matthew Wilcox wrote:
> On Fri, Mar 20, 2020 at 10:37:34AM -0700, Eric Biggers wrote:
> > On Fri, Mar 20, 2020 at 07:22:26AM -0700, Matthew Wilcox wrote:
> > > From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> > >
> > > Use the new readahead operation in ext4
> > >
> > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> > > Reviewed-by: William Kucharski <william.kucharski@oracle.com>
> > > ---
> > > fs/ext4/ext4.h | 3 +--
> > > fs/ext4/inode.c | 21 +++++++++------------
> > > fs/ext4/readpage.c | 22 ++++++++--------------
> > > 3 files changed, 18 insertions(+), 28 deletions(-)
> > >
> >
> > Reviewed-by: Eric Biggers <ebiggers@google.com>
> >
> > > + if (rac) {
> > > + page = readahead_page(rac);
> > > prefetchw(&page->flags);
> > > - list_del(&page->lru);
> > > - if (add_to_page_cache_lru(page, mapping, page->index,
> > > - readahead_gfp_mask(mapping)))
> > > - goto next_page;
> > > }
> >
> > Maybe the prefetchw(&page->flags) should be included in readahead_page()?
> > Most of the callers do it.
>
> I did notice that a lot of callers do that. I wonder whether it (still)
> helps or whether it's just cargo-cult programming. It can't possibly
> have helped before because we did list_del(&page->lru) as the very next
> instruction after prefetchw(), and they're in the same cacheline. It'd
> be interesting to take it out and see what happens to performance.
Yeah, it does look like the list_del() made the prefetchw() useless, so it
should just be removed. The prefetchw() dates all the way back to
mpage_readpages() being added in 2002, but even then the list_del() was
immediately afterwards, and 'flags' and 'lru' were in the same cache line in
'struct page' even then (assuming at least a 32-byte cache line size), so...
- Eric
next prev parent reply other threads:[~2020-03-20 18:40 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-20 14:22 [PATCH v9 00/25] Change readahead API Matthew Wilcox
2020-03-20 14:22 ` [PATCH v9 01/25] mm: Move readahead prototypes from mm.h Matthew Wilcox
2020-03-20 14:22 ` [PATCH v9 02/25] mm: Return void from various readahead functions Matthew Wilcox
2020-03-20 14:22 ` [PATCH v9 03/25] mm: Ignore return value of ->readpages Matthew Wilcox
2020-03-20 14:22 ` [PATCH v9 04/25] mm: Move readahead nr_pages check into read_pages Matthew Wilcox
2020-03-20 14:22 ` [PATCH v9 05/25] mm: Add new readahead_control API Matthew Wilcox
2020-03-20 14:22 ` [PATCH v9 06/25] mm: Use readahead_control to pass arguments Matthew Wilcox
2020-03-20 14:22 ` [PATCH v9 07/25] mm: Rename various 'offset' parameters to 'index' Matthew Wilcox
2020-03-20 14:22 ` [PATCH v9 08/25] mm: rename readahead loop variable to 'i' Matthew Wilcox
2020-03-20 14:22 ` [PATCH v9 09/25] mm: Remove 'page_offset' from readahead loop Matthew Wilcox
2020-03-20 14:22 ` [PATCH v9 10/25] mm: Put readahead pages in cache earlier Matthew Wilcox
2020-03-20 14:22 ` [PATCH v9 11/25] mm: Add readahead address space operation Matthew Wilcox
2020-03-20 14:22 ` [PATCH v9 12/25] mm: Move end_index check out of readahead loop Matthew Wilcox
2020-03-20 16:58 ` Eric Biggers
2020-03-20 17:30 ` Matthew Wilcox
2020-03-20 18:00 ` Eric Biggers
2020-03-20 18:11 ` Matthew Wilcox
2020-03-20 18:24 ` Eric Biggers
2020-03-22 16:28 ` Matthew Wilcox
2020-03-20 14:22 ` [PATCH v9 13/25] mm: Add page_cache_readahead_unbounded Matthew Wilcox
2020-03-20 17:27 ` Eric Biggers
2020-03-20 14:22 ` [PATCH v9 14/25] mm: Document why we don't set PageReadahead Matthew Wilcox
2020-03-20 14:22 ` [PATCH v9 15/25] mm: Use memalloc_nofs_save in readahead path Matthew Wilcox
2020-03-20 14:22 ` [PATCH v9 16/25] fs: Convert mpage_readpages to mpage_readahead Matthew Wilcox
2020-03-20 23:24 ` Namjae Jeon
2020-03-20 14:22 ` [PATCH v9 17/25] btrfs: Convert from readpages to readahead Matthew Wilcox
2020-03-20 14:22 ` [PATCH v9 18/25] erofs: Convert uncompressed files " Matthew Wilcox
2020-03-21 12:38 ` [f2fs-dev] " Chao Yu
2020-03-20 14:22 ` [PATCH v9 19/25] erofs: Convert compressed " Matthew Wilcox
2020-03-21 12:41 ` [f2fs-dev] " Chao Yu
2020-03-20 14:22 ` [PATCH v9 20/25] ext4: Convert " Matthew Wilcox
2020-03-20 17:37 ` Eric Biggers
2020-03-20 17:48 ` Matthew Wilcox
2020-03-20 18:40 ` Eric Biggers [this message]
2020-03-20 14:22 ` [PATCH v9 21/25] ext4: Pass the inode to ext4_mpage_readpages Matthew Wilcox
2020-03-20 18:44 ` Eric Biggers
2020-03-20 14:22 ` [PATCH v9 22/25] f2fs: Convert from readpages to readahead Matthew Wilcox
2020-03-20 18:51 ` Eric Biggers
2020-03-21 12:34 ` [f2fs-dev] " Chao Yu
2020-03-23 3:55 ` Jaegeuk Kim
2020-03-20 14:22 ` [PATCH v9 23/25] f2fs: Pass the inode to f2fs_mpage_readpages Matthew Wilcox
2020-03-20 18:52 ` Eric Biggers
2020-03-21 12:35 ` [f2fs-dev] " Chao Yu
2020-03-23 3:53 ` Jaegeuk Kim
2020-03-20 14:22 ` [PATCH v9 24/25] fuse: Convert from readpages to readahead Matthew Wilcox
2020-03-20 14:22 ` [PATCH v9 25/25] iomap: " Matthew Wilcox
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