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[ Upstream commit 2153bd1e3d ]
The SMC fallback is incomplete currently. There may be some
wait queue entries remaining in smc socket->wq, which should
be removed to clcsocket->wq during the fallback.
For example, in nginx/wrk benchmark, this issue causes an
all-zeros test result:
server: nginx -g 'daemon off;'
client: smc_run wrk -c 1 -t 1 -d 5 http://11.200.15.93/index.html
Running 5s test @ http://11.200.15.93/index.html
1 threads and 1 connections
Thread Stats Avg Stdev Max ± Stdev
Latency 0.00us 0.00us 0.00us -nan%
Req/Sec 0.00 0.00 0.00 -nan%
0 requests in 5.00s, 0.00B read
Requests/sec: 0.00
Transfer/sec: 0.00B
The reason for this all-zeros result is that when wrk used SMC
to replace TCP, it added an eppoll_entry into smc socket->wq
and expected to be notified if epoll events like EPOLL_IN/
EPOLL_OUT occurred on the smc socket.
However, once a fallback occurred, wrk switches to use clcsocket.
Now it is clcsocket->wq instead of smc socket->wq which will
be woken up. The eppoll_entry remaining in smc socket->wq does
not work anymore and wrk stops the test.
This patch fixes this issue by removing remaining wait queue
entries from smc socket->wq to clcsocket->wq during the fallback.
Link: https://www.spinics.net/lists/netdev/msg779769.html
Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
Reviewed-by: Tony Lu <tonylu@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.