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SUNRPC: Reduce thread wake-up rate when receiving large RPC messages

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With large NFS WRITE requests on TCP, I measured 5-10 thread wake-
ups to receive each request. This is because the socket layer
calls ->sk_data_ready() frequently, and each call triggers a
thread wake-up. Each recvmsg() seems to pull in less than 100KB.

Have the socket layer hold ->sk_data_ready() calls until the full
incoming message has arrived to reduce the wake-up rate.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Chuck Lever 2023-07-19 14:31:29 -04:00
parent 89d2d9fbea
commit 2b877fc53e
1 changed files with 11 additions and 1 deletions
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12
net/sunrpc/svcsock.c
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@ -1089,6 +1089,9 @@ static void svc_tcp_fragment_received(struct svc_sock *svsk)
/* If we have more data, signal svc_xprt_enqueue() to try again */ /* If we have more data, signal svc_xprt_enqueue() to try again */
svsk->sk_tcplen = 0; svsk->sk_tcplen = 0;
svsk->sk_marker = xdr_zero; svsk->sk_marker = xdr_zero;
smp_wmb();
tcp_set_rcvlowat(svsk->sk_sk, 1);
} }
/** /**
@ -1178,10 +1181,17 @@ err_incomplete:
goto err_delete; goto err_delete;
if (len == want) if (len == want)
svc_tcp_fragment_received(svsk); svc_tcp_fragment_received(svsk);
else else {
/* Avoid more ->sk_data_ready() calls until the rest
* of the message has arrived. This reduces service
* thread wake-ups on large incoming messages. */
tcp_set_rcvlowat(svsk->sk_sk,
svc_sock_reclen(svsk) - svsk->sk_tcplen);
trace_svcsock_tcp_recv_short(&svsk->sk_xprt, trace_svcsock_tcp_recv_short(&svsk->sk_xprt,
svc_sock_reclen(svsk), svc_sock_reclen(svsk),
svsk->sk_tcplen - sizeof(rpc_fraghdr)); svsk->sk_tcplen - sizeof(rpc_fraghdr));
}
goto err_noclose; goto err_noclose;
error: error:
if (len != -EAGAIN) if (len != -EAGAIN)