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| author | D. Wythe <alibuda@linux.alibaba.com> | 2023-02-02 09:26:40 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2023-02-04 10:48:19 +0100 |
| commit | f6421014e88983c5bb7a25c71c01ae6278a01df9 (patch) | |
| tree | 61e10bb4014ad23c41ed6d7c0714024cbd4c0ba1 /net | |
| parent | net/smc: llc_conf_mutex refactor, replace it with rw_semaphore (diff) | |
| download | linux-f6421014e88983c5bb7a25c71c01ae6278a01df9.tar.xz linux-f6421014e88983c5bb7a25c71c01ae6278a01df9.zip | |
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')
| -rw-r--r-- | net/smc/smc_core.c | 8 |
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; |