Re: [PATCH] net/smc: avoid atomic_set and smp_wmb in the tx path when possible
From: Dust Li <dust.li@linux.alibaba.com>
Date: 2023-11-02 14:54:28
Also in:
linux-s390
On Thu, Nov 02, 2023 at 05:27:12PM +0800, Li RongQing wrote:
these is less opportunity that conn->tx_pushing is not 1, since
these -> there ?
tx_pushing is just checked with 1, so move the setting tx_pushing to 1 after atomic_dec_and_test() return false, to avoid atomic_set and smp_wmb in tx path when possible
The patch should add [PATCH net-next] subject-prefix since this is an optimization. Besides, do you have any performance number ? Thanks
quoted hunk ↗ jump to hunk
Signed-off-by: Li RongQing <redacted> --- net/smc/smc_tx.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)diff --git a/net/smc/smc_tx.c b/net/smc/smc_tx.c index 3b0ff3b..72dbdee 100644 --- a/net/smc/smc_tx.c +++ b/net/smc/smc_tx.c@@ -667,8 +667,6 @@ int smc_tx_sndbuf_nonempty(struct smc_connection *conn)return 0; again: - atomic_set(&conn->tx_pushing, 1); - smp_wmb(); /* Make sure tx_pushing is 1 before real send */ rc = __smc_tx_sndbuf_nonempty(conn); /* We need to check whether someone else have added some data into@@ -677,8 +675,11 @@ int smc_tx_sndbuf_nonempty(struct smc_connection *conn)* If so, we need to push again to prevent those data hang in the send * queue. */ - if (unlikely(!atomic_dec_and_test(&conn->tx_pushing))) + if (unlikely(!atomic_dec_and_test(&conn->tx_pushing))) { + atomic_set(&conn->tx_pushing, 1); + smp_wmb(); /* Make sure tx_pushing is 1 before real send */ goto again; + } return rc; } -- 2.9.4