From: Christoph Hellwig <hch@infradead.org>
To: Chao Yu <chao@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>,
jaegeuk@kernel.org, linux-f2fs-devel@lists.sourceforge.net,
linux-kernel@vger.kernel.org, linux-block@vger.kernel.org
Subject: Re: [PATCH v3] f2fs: introduce flush_policy sysfs entry
Date: Tue, 12 Aug 2025 00:32:25 -0700 [thread overview]
Message-ID: <aJruCTOjcj1nEk-S@infradead.org> (raw)
In-Reply-To: <c5195d5c-5f71-4057-9522-228b48e4cd90@kernel.org>
On Tue, Aug 12, 2025 at 02:28:46PM +0800, Chao Yu wrote:
> BTW, I suffered extremely long latency of checkpoint which may block every
> update operations when testing generic/299 w/ mode=lfs mount option in qemu,
> then I propose to use PREFLUSH instead of FUA to resolve this issue.
>
> "F2FS-fs (vdc): checkpoint was blocked for 24495 ms"
>
> I just realize that using cache=directsync option in qemu can avoid FUA hang
> issue, anyway, let me test more w/ this option.
Well, for decent qemu performance you always want to use DIRECT I/O.
directsync is generally not a very good idea as it forces every write
to be synchronous and will give you very bad performance.
What did you use before? At least for older qemu the default was
buffered I/O, which can lead to very expensive fua or flush calls.
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org>
To: Chao Yu <chao@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>,
jaegeuk@kernel.org, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org,
linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH v3] f2fs: introduce flush_policy sysfs entry
Date: Tue, 12 Aug 2025 00:32:25 -0700 [thread overview]
Message-ID: <aJruCTOjcj1nEk-S@infradead.org> (raw)
In-Reply-To: <c5195d5c-5f71-4057-9522-228b48e4cd90@kernel.org>
On Tue, Aug 12, 2025 at 02:28:46PM +0800, Chao Yu wrote:
> BTW, I suffered extremely long latency of checkpoint which may block every
> update operations when testing generic/299 w/ mode=lfs mount option in qemu,
> then I propose to use PREFLUSH instead of FUA to resolve this issue.
>
> "F2FS-fs (vdc): checkpoint was blocked for 24495 ms"
>
> I just realize that using cache=directsync option in qemu can avoid FUA hang
> issue, anyway, let me test more w/ this option.
Well, for decent qemu performance you always want to use DIRECT I/O.
directsync is generally not a very good idea as it forces every write
to be synchronous and will give you very bad performance.
What did you use before? At least for older qemu the default was
buffered I/O, which can lead to very expensive fua or flush calls.
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https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
next prev parent reply other threads:[~2025-08-12 7:32 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-07 3:48 [f2fs-dev] [PATCH v3] f2fs: introduce flush_policy sysfs entry Chao Yu via Linux-f2fs-devel
2025-08-07 3:48 ` Chao Yu
2025-08-07 5:31 ` [f2fs-dev] " Zhiguo Niu
2025-08-07 5:31 ` Zhiguo Niu
2025-08-11 10:52 ` Christoph Hellwig
2025-08-11 10:52 ` [f2fs-dev] " Christoph Hellwig
2025-08-11 13:44 ` Bart Van Assche
2025-08-11 13:44 ` [f2fs-dev] " Bart Van Assche via Linux-f2fs-devel
2025-08-12 6:39 ` Chao Yu
2025-08-12 6:39 ` [f2fs-dev] " Chao Yu via Linux-f2fs-devel
2025-08-12 6:28 ` Chao Yu
2025-08-12 6:28 ` [f2fs-dev] " Chao Yu via Linux-f2fs-devel
2025-08-12 7:32 ` Christoph Hellwig [this message]
2025-08-12 7:32 ` Christoph Hellwig
2025-08-12 7:53 ` Chao Yu
2025-08-12 7:53 ` [f2fs-dev] " Chao Yu via Linux-f2fs-devel
2025-08-12 7:59 ` Christoph Hellwig
2025-08-12 7:59 ` [f2fs-dev] " Christoph Hellwig
2025-08-12 8:22 ` Chao Yu
2025-08-12 8:22 ` [f2fs-dev] " Chao Yu via Linux-f2fs-devel
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