From: "hch@infradead.org" <hch@infradead.org>
To: Qu Wenruo <quwenruo.btrfs@gmx.com>
Cc: Johannes Thumshirn <Johannes.Thumshirn@wdc.com>,
WenRuo Qu <wqu@suse.com>, "hch@infradead.org" <hch@infradead.org>,
"linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>,
"djwong@kernel.org" <djwong@kernel.org>,
"linux-xfs@vger.kernel.org" <linux-xfs@vger.kernel.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"martin.petersen@oracle.com" <martin.petersen@oracle.com>,
"jack@suse.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 22:04:47 -0700 [thread overview]
Message-ID: <aPhl7wvyZ8b7cnLw@infradead.org> (raw)
In-Reply-To: <f13c9393-1733-4f52-a879-94cdc7a724f2@gmx.com>
On Wed, Oct 22, 2025 at 12:57:51PM +1030, Qu Wenruo wrote:
> My VM is using kvm64 CPU type, which blocks quite a lot of CPU features,
> thus the CRC32 performance is pretty poor.
Yes, unaccelerated CRC32 is a bad idea.
>
> I just tried a short hack to always make direct IO to fallback to buffered
> IO, the nodatasum performance is the same as the bouncing page solution, so
> the slow down is not page cache itself but really the checksum.
>
> With CPU features all passed to the VM, the falling-back-to-buffered direct
> IO performance is only slightly worse (10~20%) than nodatasum cases.
I'm a bit lost, what are the exact cases you are comparing here?
next prev parent reply other threads:[~2025-10-22 5:04 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1ee861df6fbd8bf45ab42154f429a31819294352.1760951886.git.wqu@suse.com>
2025-10-20 10:00 ` O_DIRECT vs BLK_FEAT_STABLE_WRITES, was Re: [PATCH] btrfs: never trust the bio from direct IO 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
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 [this message]
2025-10-22 6:17 ` Qu Wenruo
2025-10-22 6:24 ` hch
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