diff options
author | D. Wythe <alibuda@linux.alibaba.com> | 2023-02-02 16:26:41 +0800 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2023-02-04 09:48:19 +0000 |
commit | 4da687448de7b51dcca9d024c6049fa223f5363f (patch) | |
tree | 22cc36871439c81d4867f08ae90d789f84e74853 /net/smc/af_smc.c | |
parent | f6421014e88983c5bb7a25c71c01ae6278a01df9 (diff) |
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/af_smc.c')
-rw-r--r-- | net/smc/af_smc.c | 19 |
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; } |