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net/smc: Transfer remaining wait queue entries during fallback
[ 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>
This commit is contained in:
parent
cc447c1e14
commit
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1 changed files with 14 additions and 0 deletions
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@ -548,6 +548,10 @@ static void smc_stat_fallback(struct smc_sock *smc)
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static void smc_switch_to_fallback(struct smc_sock *smc, int reason_code)
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{
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wait_queue_head_t *smc_wait = sk_sleep(&smc->sk);
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wait_queue_head_t *clc_wait = sk_sleep(smc->clcsock->sk);
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unsigned long flags;
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smc->use_fallback = true;
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smc->fallback_rsn = reason_code;
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smc_stat_fallback(smc);
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@ -556,6 +560,16 @@ static void smc_switch_to_fallback(struct smc_sock *smc, int reason_code)
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smc->clcsock->file->private_data = smc->clcsock;
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smc->clcsock->wq.fasync_list =
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smc->sk.sk_socket->wq.fasync_list;
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/* There may be some entries remaining in
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* smc socket->wq, which should be removed
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* to clcsocket->wq during the fallback.
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*/
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spin_lock_irqsave(&smc_wait->lock, flags);
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spin_lock(&clc_wait->lock);
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list_splice_init(&smc_wait->head, &clc_wait->head);
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spin_unlock(&clc_wait->lock);
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spin_unlock_irqrestore(&smc_wait->lock, flags);
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}
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}
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