From: Christoph Hellwig <hch@infradead.org>
To: "Christian König" <christian.koenig@amd.com>
Cc: Christoph Hellwig <hch@infradead.org>,
wangtao <tao.wangtao@honor.com>,
sumit.semwal@linaro.org, kraxel@redhat.com,
vivek.kasireddy@intel.com, viro@zeniv.linux.org.uk,
brauner@kernel.org, hughd@google.com, akpm@linux-foundation.org,
amir73il@gmail.com, benjamin.gaignard@collabora.com,
Brian.Starkey@arm.com, jstultz@google.com, tjmercier@google.com,
jack@suse.cz, baolin.wang@linux.alibaba.com,
linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
bintian.wang@honor.com, yipengxiang@honor.com,
liulu.liu@honor.com, feng.han@honor.com
Subject: Re: [PATCH v4 0/4] Implement dmabuf direct I/O via copy_file_range
Date: Tue, 3 Jun 2025 07:28:27 -0700 [thread overview]
Message-ID: <aD8Gi9ShWDEYqWjB@infradead.org> (raw)
In-Reply-To: <924ac01f-b86b-4a03-b563-878fa7736712@amd.com>
On Tue, Jun 03, 2025 at 04:18:22PM +0200, Christian König wrote:
> > Does it matter compared to the I/O in this case?
>
> It unfortunately does, see the numbers on patch 3 and 4.
That's kinda weird. Why does the page table lookup tage so much
time compared to normal I/O?
> My question is rather if it's ok to call f_op->write_iter() and
> f_op->read_iter() with pages allocated by alloc_pages(), e.g.
> where drivers potentially ignore the page count and just re-use pages
> as they like?
read_iter and write_iter with ITER_BVEC just use the pages as source
and destination of the I/O. They must not touch the refcounts or
do anything fancy with them. Various places in the kernel rely on
that.
next prev parent reply other threads:[~2025-06-03 14:28 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-03 9:52 [PATCH v4 0/4] Implement dmabuf direct I/O via copy_file_range wangtao
2025-06-03 9:52 ` [PATCH v4 1/4] fs: allow cross-FS copy_file_range for memory file with direct I/O wangtao
2025-06-03 10:56 ` Amir Goldstein
2025-06-03 12:38 ` wangtao
2025-06-03 12:43 ` Amir Goldstein
2025-06-03 9:52 ` [PATCH v4 2/4] dmabuf: Implement copy_file_range callback for dmabuf direct I/O prep wangtao
2025-06-03 10:42 ` Christian König
2025-06-03 12:26 ` wangtao
2025-06-03 13:04 ` Christoph Hellwig
2025-06-03 9:52 ` [PATCH v4 3/4] udmabuf: Implement udmabuf direct I/O wangtao
2025-06-03 9:52 ` [PATCH v4 4/4] dmabuf:system_heap Implement system_heap dmabuf " wangtao
2025-06-03 13:00 ` [PATCH v4 0/4] Implement dmabuf direct I/O via copy_file_range Christoph Hellwig
2025-06-03 13:14 ` Christian König
2025-06-03 13:19 ` Christoph Hellwig
2025-06-03 14:18 ` Christian König
2025-06-03 14:28 ` Christoph Hellwig [this message]
2025-06-03 15:55 ` Christian König
2025-06-03 16:01 ` Christoph Hellwig
2025-06-06 9:59 ` wangtao
2025-06-06 9:52 ` wangtao
2025-06-06 11:20 ` Christian König
2025-06-09 4:35 ` Christoph Hellwig
2025-06-09 9:32 ` wangtao
2025-06-10 10:52 ` Christian König
2025-06-10 13:37 ` Christoph Hellwig
2025-06-13 9:43 ` wangtao
2025-06-16 5:24 ` Christoph Hellwig
2025-06-10 13:34 ` Christoph Hellwig
2025-06-13 9:33 ` wangtao
2025-06-16 5:25 ` Christoph Hellwig
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