Re: [PATCH v2 net] splice: do not checksum AF_UNIX sockets

On Tue, Dec 10, 2024 at 6:06 AM Frederik Deweerdt deweerdt.lkml@gmail.com wrote:

When `skb_splice_from_iter` was introduced, it inadvertently added checksumming for AF_UNIX sockets. This resulted in significant slowdowns, for example when using sendfile over unix sockets.

Using the test code in [1] in my test setup (2G single core qemu), the client receives a 1000M file in:

• without the patch: 1482ms (+/- 36ms)
• with the patch: 652.5ms (+/- 22.9ms)

This commit addresses the issue by marking checksumming as unnecessary in `unix_stream_sendmsg`

Cc: stable@vger.kernel.org Signed-off-by: Frederik Deweerdt deweerdt.lkml@gmail.com Fixes: 2e910b95329c ("net: Add a function to splice pages into an skbuff for MSG_SPLICE_PAGES")

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Reviewed-by: Eric Dumazet edumazet@google.com