From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E0DF31DE4CE for ; Mon, 28 Jul 2025 08:07:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753690052; cv=none; b=p+xWpjC/DViRaixrRtdyvtDjLkthsuiuPCU9CJxCmCDG83UmQSbn2vNbV0pWKXaKs+VmBtJSyw5p93rBq5Q+dQxdW6sJPB1n83taSwWjkrv3whh8m92PJCNwGLbRprOV0zShmYvedNFVZvaWrHTz2b86FePzxNe1DG8x34Rm4Y4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753690052; c=relaxed/simple; bh=lqV0tgABHCNr5zK2W1ACEsPKJu5VpCezF5PxxjLbB6Y=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=HLO63ZCYoU+2zv9hGy/o3oIdFhU9Nmr/dOwNf3aNtdj7BojKtliSXDn06lQX3pygtFAf79rQVAPh7o25VBuKbVU/EnNHw1rbOsXnDWPBt8A7QT0zAmSmpHdDCpL2CyE0jPfBIknvI1Se5+tnvhJCRVPy3f1qcW0ZiYFKZScqF7g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Md83gGme; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Md83gGme" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D925FC4CEE7; Mon, 28 Jul 2025 08:07:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1753690051; bh=lqV0tgABHCNr5zK2W1ACEsPKJu5VpCezF5PxxjLbB6Y=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=Md83gGme9scPaWP59ypo3l5IxBv1vqyDU4N3bnl2ZwkUPo/+XyaQe8Q5bbVR4WX45 tMAVTu9b6JfLKhcLMEeCdEvue1LDWriemaFvSxuZO/NQ/v3Q8rBBuExa/Tzd56vCMk 0PHh+beicfcBemckzfVQDy39K5EJbGD58ajOKEaDuW9Kspm9b6SROInptA6CIyuFWj GtFPlWHOl8jcdtH84AHuNy2onOm01w/+ILbGENyGR+E+uuqhUs44mnbJswTzbqAao/ urGqNggSBkLn+E4RWT8ky2EY2udmrrdvcxszwMMXFAXOlEpcmKI1NUHO2PEwTfcQM8 d6JDuKBV+KjQQ== Message-ID: <087f7937-20b5-4151-8a3f-5b6b2b045b41@kernel.org> Date: Mon, 28 Jul 2025 16:07:27 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: chao@kernel.org, axboe@kernel.dk, linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH] f2fs: f2fs supports uncached buffered I/O read To: hanqi , jaegeuk@kernel.org References: <20250725075310.1614614-1-hanqi@vivo.com> Content-Language: en-US From: Chao Yu In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 7/28/25 16:03, hanqi wrote: > 在 2025/7/28 15:38, Chao Yu 写道: > >> On 7/25/25 15:53, Qi Han wrote: >>> Jens has already completed the development of uncached buffered I/O >>> in git [1], and in f2fs, uncached buffered I/O read can be enabled >>> simply by setting the FOP_DONTCACHE flag in f2fs_file_operations. >> IIUC, we may suffer lock issue when we call pwritev(.. ,RWF_DONTCACHE)? >> as Jen mentioned in below path, right? >> >> soft-irq >> - folio_end_writeback() >>   - filemap_end_dropbehind_write() >>    - filemap_end_dropbehind() >>     - folio_unmap_invalidate() >>      - lock i_lock >> >> Thanks, > > That's how I understand it. So I guess we need to wait for the support RWF_DONTCACHE on write path, unless you can walk around for write path in this patch. Thanks, > >>> I have been testing a use case locally, which aligns with Jens' test >>> case [2]. In the read scenario, using uncached buffer I/O results in >>> more stable read performance and a lower load on the background memory >>> reclaim thread (kswapd). So let's enable uncached buffer I/O reads on >>> F2FS. >>> >>> Read test data without using uncached buffer I/O: >>> reading bs 32768, uncached 0 >>>     1s: 1856MB/sec, MB=1856 >>>     2s: 1907MB/sec, MB=3763 >>>     3s: 1830MB/sec, MB=5594 >>>     4s: 1745MB/sec, MB=7333 >>>     5s: 1829MB/sec, MB=9162 >>>     6s: 1903MB/sec, MB=11075 >>>     7s: 1878MB/sec, MB=12942 >>>     8s: 1763MB/sec, MB=14718 >>>     9s: 1845MB/sec, MB=16549 >>>    10s: 1915MB/sec, MB=18481 >>>    11s: 1831MB/sec, MB=20295 >>>    12s: 1750MB/sec, MB=22066 >>>    13s: 1787MB/sec, MB=23832 >>>    14s: 1913MB/sec, MB=25769 >>>    15s: 1898MB/sec, MB=27668 >>>    16s: 1795MB/sec, MB=29436 >>>    17s: 1812MB/sec, MB=31248 >>>    18s: 1890MB/sec, MB=33139 >>>    19s: 1880MB/sec, MB=35020 >>>    20s: 1754MB/sec, MB=36810 >>> >>> 08:36:26      UID       PID    %usr %system  %guest   %wait    %CPU   CPU  Command >>> 08:36:27        0        93    0.00    0.00    0.00    0.00    0.00     7  kswapd0 >>> 08:36:28        0        93    0.00    0.00    0.00    0.00    0.00     7  kswapd0 >>> 08:36:29        0        93    0.00    0.00    0.00    0.00    0.00     7  kswapd0 >>> 08:36:30        0        93    0.00   56.00    0.00    0.00   56.00     7  kswapd0 >>> 08:36:31        0        93    0.00   73.00    0.00    0.00   73.00     7  kswapd0 >>> 08:36:32        0        93    0.00   83.00    0.00    0.00   83.00     7  kswapd0 >>> 08:36:33        0        93    0.00   75.00    0.00    0.00   75.00     7  kswapd0 >>> 08:36:34        0        93    0.00   81.00    0.00    0.00   81.00     7  kswapd0 >>> 08:36:35        0        93    0.00   54.00    0.00    1.00   54.00     2  kswapd0 >>> 08:36:36        0        93    0.00   61.00    0.00    0.00   61.00     0  kswapd0 >>> 08:36:37        0        93    0.00   68.00    0.00    0.00   68.00     7  kswapd0 >>> 08:36:38        0        93    0.00   53.00    0.00    0.00   53.00     2  kswapd0 >>> 08:36:39        0        93    0.00   82.00    0.00    0.00   82.00     7  kswapd0 >>> 08:36:40        0        93    0.00   77.00    0.00    0.00   77.00     1  kswapd0 >>> 08:36:41        0        93    0.00   74.00    0.00    1.00   74.00     7  kswapd0 >>> 08:36:42        0        93    0.00   71.00    0.00    0.00   71.00     7  kswapd0 >>> 08:36:43        0        93    0.00   78.00    0.00    0.00   78.00     7  kswapd0 >>> 08:36:44        0        93    0.00   85.00    0.00    0.00   85.00     7  kswapd0 >>> 08:36:45        0        93    0.00   83.00    0.00    0.00   83.00     7  kswapd0 >>> 08:36:46        0        93    0.00   70.00    0.00    0.00   70.00     7  kswapd0 >>> 08:36:47        0        93    0.00   78.00    0.00    1.00   78.00     2  kswapd0 >>> 08:36:48        0        93    0.00   81.00    0.00    0.00   81.00     3  kswapd0 >>> 08:36:49        0        93    0.00   54.00    0.00    0.00   54.00     7  kswapd0 >>> 08:36:50        0        93    0.00   76.00    0.00    0.00   76.00     1  kswapd0 >>> 08:36:51        0        93    0.00   75.00    0.00    0.00   75.00     0  kswapd0 >>> 08:36:52        0        93    0.00   73.00    0.00    0.00   73.00     7  kswapd0 >>> 08:36:53        0        93    0.00   61.00    0.00    1.00   61.00     7  kswapd0 >>> 08:36:54        0        93    0.00   80.00    0.00    0.00   80.00     7  kswapd0 >>> 08:36:55        0        93    0.00   64.00    0.00    0.00   64.00     7  kswapd0 >>> 08:36:56        0        93    0.00   56.00    0.00    0.00   56.00     7  kswapd0 >>> 08:36:57        0        93    0.00   26.00    0.00    0.00   26.00     2  kswapd0 >>> 08:36:58        0        93    0.00   24.00    0.00    1.00   24.00     3  kswapd0 >>> 08:36:59        0        93    0.00   22.00    0.00    1.00   22.00     3  kswapd0 >>> 08:37:00        0        93    0.00   15.84    0.00    0.00   15.84     3  kswapd0 >>> 08:37:01        0        93    0.00    0.00    0.00    0.00    0.00     3  kswapd0 >>> 08:37:02        0        93    0.00    0.00    0.00    0.00    0.00     3  kswapd0 >>> >>> Read test data after using uncached buffer I/O: >>> reading bs 32768, uncached 1 >>>     1s: 1863MB/sec, MB=1863 >>>     2s: 1903MB/sec, MB=3766 >>>     3s: 1860MB/sec, MB=5627 >>>     4s: 1864MB/sec, MB=7491 >>>     5s: 1860MB/sec, MB=9352 >>>     6s: 1854MB/sec, MB=11206 >>>     7s: 1874MB/sec, MB=13081 >>>     8s: 1874MB/sec, MB=14943 >>>     9s: 1840MB/sec, MB=16798 >>>    10s: 1849MB/sec, MB=18647 >>>    11s: 1863MB/sec, MB=20511 >>>    12s: 1798MB/sec, MB=22310 >>>    13s: 1897MB/sec, MB=24207 >>>    14s: 1817MB/sec, MB=26025 >>>    15s: 1893MB/sec, MB=27918 >>>    16s: 1917MB/sec, MB=29836 >>>    17s: 1863MB/sec, MB=31699 >>>    18s: 1904MB/sec, MB=33604 >>>    19s: 1894MB/sec, MB=35499 >>>    20s: 1907MB/sec, MB=37407 >>> >>> 08:38:00      UID       PID    %usr %system  %guest   %wait    %CPU   CPU  Command >>> 08:38:01        0        93    0.00    0.00    0.00    0.00    0.00     4  kswapd0 >>> 08:38:02        0        93    0.00    0.00    0.00    0.00    0.00     4  kswapd0 >>> 08:38:03        0        93    0.00    0.00    0.00    0.00    0.00     4  kswapd0 >>> 08:38:04        0        93    0.00    0.00    0.00    0.00    0.00     4  kswapd0 >>> 08:38:05        0        93    0.00    0.00    0.00    0.00    0.00     4  kswapd0 >>> 08:38:06        0        93    0.00    1.00    0.00    1.00    1.00     0  kswapd0 >>> 08:38:07        0        93    0.00    0.00    0.00    0.00    0.00     0  kswapd0 >>> 08:38:08        0        93    0.00    0.00    0.00    0.00    0.00     0  kswapd0 >>> 08:38:09        0        93    0.00    1.00    0.00    0.00    1.00     1  kswapd0 >>> 08:38:10        0        93    0.00    0.00    0.00    0.00    0.00     1  kswapd0 >>> 08:38:11        0        93    0.00    0.00    0.00    0.00    0.00     1  kswapd0 >>> 08:38:12        0        93    0.00    0.00    0.00    0.00    0.00     1  kswapd0 >>> 08:38:13        0        93    0.00    0.00    0.00    0.00    0.00     1  kswapd0 >>> 08:38:14        0        93    0.00    0.00    0.00    0.00    0.00     1  kswapd0 >>> 08:38:15        0        93    0.00    3.00    0.00    0.00    3.00     0  kswapd0 >>> 08:38:16        0        93    0.00    0.00    0.00    0.00    0.00     0  kswapd0 >>> 08:38:17        0        93    0.00    0.00    0.00    0.00    0.00     0  kswapd0 >>> 08:38:18        0        93    0.00    0.00    0.00    0.00    0.00     0  kswapd0 >>> 08:38:19        0        93    0.00    0.00    0.00    0.00    0.00     0  kswapd0 >>> 08:38:20        0        93    0.00    0.00    0.00    0.00    0.00     0  kswapd0 >>> 08:38:21        0        93    0.00    0.00    0.00    0.00    0.00     0  kswapd0 >>> 08:38:22        0        93    0.00    0.00    0.00    0.00    0.00     0  kswapd0 >>> 08:38:23        0        93    0.00    3.00    0.00    0.00    3.00     4  kswapd0 >>> 08:38:24        0        93    0.00    0.00    0.00    0.00    0.00     4  kswapd0 >>> 08:38:25        0        93    0.00    0.00    0.00    0.00    0.00     4  kswapd0 >>> 08:38:26        0        93    0.00    4.00    0.00    0.00    4.00     3  kswapd0 >>> 08:38:27        0        93    0.00    0.00    0.00    0.00    0.00     3  kswapd0 >>> 08:38:28        0        93    0.00    0.00    0.00    0.00    0.00     3  kswapd0 >>> 08:38:29        0        93    0.00    0.00    0.00    0.00    0.00     3  kswapd0 >>> 08:38:30        0        93    0.00    0.00    0.00    0.00    0.00     3  kswapd0 >>> 08:38:31        0        93    0.00    0.00    0.00    0.00    0.00     3  kswapd0 >>> 08:38:32        0        93    0.00    0.00    0.00    0.00    0.00     3  kswapd0 >>> 08:38:33        0        93    0.00    0.00    0.00    0.00    0.00     3  kswapd0 >>> >>> [1] >>> https://lore.kernel.org/all/20241220154831.1086649-10-axboe@kernel.dk/T/#m58520a94b46f543d82db3711453dfc7bb594b2b0 >>> >>> [2] >>> https://pastebin.com/u8eCBzB5 >>> >>> Signed-off-by: Qi Han >>> --- >>>   fs/f2fs/file.c | 2 +- >>>   1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c >>> index 696131e655ed..d8da1fc2febf 100644 >>> --- a/fs/f2fs/file.c >>> +++ b/fs/f2fs/file.c >>> @@ -5425,5 +5425,5 @@ const struct file_operations f2fs_file_operations = { >>>       .splice_read    = f2fs_file_splice_read, >>>       .splice_write    = iter_file_splice_write, >>>       .fadvise    = f2fs_file_fadvise, >>> -    .fop_flags    = FOP_BUFFER_RASYNC, >>> +    .fop_flags    = FOP_BUFFER_RASYNC | FOP_DONTCACHE, >>>   }; >