From: Christoph Hellwig <hch@infradead.org>
To: Qu Wenruo <quwenruo.btrfs@gmx.com>
Cc: Christoph Hellwig <hch@infradead.org>, Qu Wenruo <wqu@suse.com>,
linux-btrfs@vger.kernel.org, djwong@kernel.org,
linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-block@vger.kernel.org, linux-mm@kvack.org,
martin.petersen@oracle.com, jack@suse.com
Subject: Re: O_DIRECT vs BLK_FEAT_STABLE_WRITES, was Re: [PATCH] btrfs: never trust the bio from direct IO
Date: Tue, 21 Oct 2025 00:48:08 -0700 [thread overview]
Message-ID: <aPc6uLKJkavZ_SkM@infradead.org> (raw)
In-Reply-To: <b91eb17a-71ce-422c-99a1-c2970a015666@gmx.com>
On Tue, Oct 21, 2025 at 01:47:03PM +1030, Qu Wenruo wrote:
> Off-topic a little, mind to share the performance drop with PI enabled on
> XFS?
If the bandwith of the SSDs get close or exceeds the DRAM bandwith
buffered I/O can be 50% or less of the direct I/O performance.
> With this patch I'm able to enable direct IO for inodes with checksums.
> I thought it would easily improve the performance, but the truth is, it's
> not that different from buffered IO fall back.
That's because you still copy data.
> So I start wondering if it's the checksum itself causing the miserable
> performance numbers.
Only indirectly by touching all the cachelines. But once you copy you
touch them again. Especially if not done in small chunks.
next prev parent reply other threads:[~2025-10-21 7:48 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-20 9:19 [PATCH] btrfs: never trust the bio from direct IO Qu Wenruo
2025-10-20 10:00 ` O_DIRECT vs BLK_FEAT_STABLE_WRITES, was " Christoph Hellwig
2025-10-20 10:24 ` Qu Wenruo
2025-10-20 11:45 ` Christoph Hellwig
2025-10-20 11:16 ` Jan Kara
2025-10-20 11:44 ` Christoph Hellwig
2025-10-20 13:59 ` Jan Kara
2025-10-20 14:59 ` Matthew Wilcox
2025-10-20 15:58 ` Jan Kara
2025-10-20 17:55 ` John Hubbard
2025-10-21 8:27 ` Jan Kara
2025-10-21 16:56 ` John Hubbard
2025-10-20 19:00 ` David Hildenbrand
2025-10-21 7:49 ` Christoph Hellwig
2025-10-21 7:57 ` David Hildenbrand
2025-10-21 9:33 ` Jan Kara
2025-10-21 9:43 ` David Hildenbrand
2025-10-21 9:22 ` Jan Kara
2025-10-21 9:37 ` David Hildenbrand
2025-10-21 9:52 ` Jan Kara
2025-10-21 3:17 ` Qu Wenruo
2025-10-21 7:48 ` Christoph Hellwig [this message]
2025-10-21 8:15 ` Qu Wenruo
2025-10-21 11:30 ` Johannes Thumshirn
2025-10-22 2:27 ` Qu Wenruo
2025-10-22 5:04 ` hch
2025-10-22 6:17 ` Qu Wenruo
2025-10-22 6:24 ` hch
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