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: 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
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=aPhl7wvyZ8b7cnLw@infradead.org \
--to=hch@infradead.org \
--cc=Johannes.Thumshirn@wdc.com \
--cc=djwong@kernel.org \
--cc=jack@suse.com \
--cc=linux-block@vger.kernel.org \
--cc=linux-btrfs@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-xfs@vger.kernel.org \
--cc=martin.petersen@oracle.com \
--cc=quwenruo.btrfs@gmx.com \
--cc=wqu@suse.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.