On 9/15/21 8:47 AM, Alan Somers wrote:
On Wed, Sep 15, 2021 at 9:21 AM John Baldwin <j...@freebsd.org> wrote:
On 9/14/21 1:53 PM, Alan Somers wrote:
On Tue, Sep 14, 2021 at 2:46 PM John Baldwin <j...@freebsd.org> wrote:
The branch main has been updated by jhb:
URL:
https://cgit.FreeBSD.org/src/commit/?id=1ecbc1d8e9d3fbcd8e68fc68f0a32944a12ddb1e
commit 1ecbc1d8e9d3fbcd8e68fc68f0a32944a12ddb1e
Author: John Baldwin <j...@freebsd.org>
AuthorDate: 2021-09-14 20:46:14 +0000
Commit: John Baldwin <j...@freebsd.org>
CommitDate: 2021-09-14 20:46:14 +0000
cxgbe tom: Don't queue AIO requests on listen sockets.
This is similar to the fixes in 141fe2dceeae. One difference is
that
TOE sockets do not change states (listen vs non-listen) once
created,
so no lock is needed for SOLISTENING().
Sponsored by: Chelsio Communications
I've always wondered: what's the point to using AIO with sockets? Can't
everything socket-related be done better with non-blocking read/write and
kqueue?
Zero-copy operation with TOE is why TOE uses AIO. Zero-copy of user
buffers
can't really work with the non-AIO APIs because the user buffer is free to
be reused immediately after write(2) (and on the read side you don't know
the buffer in advance to allow the NIC to write directly into the use
buffer).
In theory we could support zero-copy using mb_ext_pgs for aio_write() for
the non-TOE case similar to what sendfile() does.
--
John Baldwin
Interesting. Do you know of any common applications that include this
optimization? I've been working on the AIO ecosystem for Rust. It would
be good to ensure that this use case works, especially if zero-copy ever
works for non-TOE.
I do not, and I rely on patches I merged upstream to netperf (-a and -A flags)
to test it. I believe there might be some proprietary bits in some FreeBSD
downstreams that might make use of this.
--
John Baldwin
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