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authorD. Wythe <alibuda@linux.alibaba.com>2023-02-02 16:26:40 +0800
committerDavid S. Miller <davem@davemloft.net>2023-02-04 09:48:19 +0000
commitf6421014e88983c5bb7a25c71c01ae6278a01df9 (patch)
tree61e10bb4014ad23c41ed6d7c0714024cbd4c0ba1 /net/smc
parentb5dd4d6981717f7e2682c0419fe832328c7441cf (diff)
net/smc: use read semaphores to reduce unnecessary blocking in smc_buf_create() & smcr_buf_unuse()
Following is part of Off-CPU graph during frequent SMC-R short-lived processing: process_one_work (51.19%) smc_close_passive_work (28.36%) smcr_buf_unuse (28.34%) rwsem_down_write_slowpath (28.22%) smc_listen_work (22.83%) smc_clc_wait_msg (1.84%) smc_buf_create (20.45%) smcr_buf_map_usable_links rwsem_down_write_slowpath (20.43%) smcr_lgr_reg_rmbs (0.53%) rwsem_down_write_slowpath (0.43%) smc_llc_do_confirm_rkey (0.08%) We can clearly see that during the connection establishment time, waiting time of connections is not on IO, but on llc_conf_mutex. What is more important, the core critical area (smcr_buf_unuse() & smc_buf_create()) only perfroms read semantics on links, we can easily replace it with read semaphore. Signed-off-by: D. Wythe <alibuda@linux.alibaba.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/smc')
-rw-r--r--net/smc/smc_core.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index 22ddce66d3ff..10a9e094d9d3 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -1106,10 +1106,10 @@ static void smcr_buf_unuse(struct smc_buf_desc *buf_desc, bool is_rmb,
rc = smc_llc_flow_initiate(lgr, SMC_LLC_FLOW_RKEY);
if (!rc) {
/* protect against smc_llc_cli_rkey_exchange() */
- down_write(&lgr->llc_conf_mutex);
+ down_read(&lgr->llc_conf_mutex);
smc_llc_do_delete_rkey(lgr, buf_desc);
buf_desc->is_conf_rkey = false;
- up_write(&lgr->llc_conf_mutex);
+ up_read(&lgr->llc_conf_mutex);
smc_llc_flow_stop(lgr, &lgr->llc_flow_lcl);
}
}
@@ -2247,7 +2247,7 @@ static int smcr_buf_map_usable_links(struct smc_link_group *lgr,
int i, rc = 0, cnt = 0;
/* protect against parallel link reconfiguration */
- down_write(&lgr->llc_conf_mutex);
+ down_read(&lgr->llc_conf_mutex);
for (i = 0; i < SMC_LINKS_PER_LGR_MAX; i++) {
struct smc_link *lnk = &lgr->lnk[i];
@@ -2260,7 +2260,7 @@ static int smcr_buf_map_usable_links(struct smc_link_group *lgr,
cnt++;
}
out:
- up_write(&lgr->llc_conf_mutex);
+ up_read(&lgr->llc_conf_mutex);
if (!rc && !cnt)
rc = -EINVAL;
return rc;