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authorD. Wythe <alibuda@linux.alibaba.com>2023-02-02 11:26:41 +0300
committerDavid S. Miller <davem@davemloft.net>2023-02-04 12:48:19 +0300
commit4da687448de7b51dcca9d024c6049fa223f5363f (patch)
tree22cc36871439c81d4867f08ae90d789f84e74853 /net/smc
parentf6421014e88983c5bb7a25c71c01ae6278a01df9 (diff)
downloadlinux-4da687448de7b51dcca9d024c6049fa223f5363f.tar.xz
net/smc: reduce unnecessary blocking in smcr_lgr_reg_rmbs()
Unlike smc_buf_create() and smcr_buf_unuse(), smcr_lgr_reg_rmbs() is exclusive when assigned rmb_desc was not registered, although it can be executed in parallel when assigned rmb_desc was registered already and only performs read semtamics on it. Hence, we can not simply replace it with read semaphore. The idea here is that if the assigned rmb_desc was registered already, use read semaphore to protect the critical section, once the assigned rmb_desc was not registered, keep using keep write semaphore still to keep its exclusivity. Thanks to the reusable features of rmb_desc, which allows us to execute in parallel in most cases. 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/af_smc.c19
1 files changed, 17 insertions, 2 deletions
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 6e93ad61d6a2..b163266e581a 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -519,11 +519,26 @@ static int smcr_lgr_reg_rmbs(struct smc_link *link,
struct smc_buf_desc *rmb_desc)
{
struct smc_link_group *lgr = link->lgr;
+ bool do_slow = false;
int i, rc = 0;
rc = smc_llc_flow_initiate(lgr, SMC_LLC_FLOW_RKEY);
if (rc)
return rc;
+
+ down_read(&lgr->llc_conf_mutex);
+ for (i = 0; i < SMC_LINKS_PER_LGR_MAX; i++) {
+ if (!smc_link_active(&lgr->lnk[i]))
+ continue;
+ if (!rmb_desc->is_reg_mr[link->link_idx]) {
+ up_read(&lgr->llc_conf_mutex);
+ goto slow_path;
+ }
+ }
+ /* mr register already */
+ goto fast_path;
+slow_path:
+ do_slow = true;
/* protect against parallel smc_llc_cli_rkey_exchange() and
* parallel smcr_link_reg_buf()
*/
@@ -535,7 +550,7 @@ static int smcr_lgr_reg_rmbs(struct smc_link *link,
if (rc)
goto out;
}
-
+fast_path:
/* exchange confirm_rkey msg with peer */
rc = smc_llc_do_confirm_rkey(link, rmb_desc);
if (rc) {
@@ -544,7 +559,7 @@ static int smcr_lgr_reg_rmbs(struct smc_link *link,
}
rmb_desc->is_conf_rkey = true;
out:
- up_write(&lgr->llc_conf_mutex);
+ do_slow ? up_write(&lgr->llc_conf_mutex) : up_read(&lgr->llc_conf_mutex);
smc_llc_flow_stop(lgr, &lgr->llc_flow_lcl);
return rc;
}