We create a lock-less link list for the currently idle reusable smc_buf_desc. When the 'used' filed mark to 0, it is added to the lock-less linked list. When a new connection is established, a suitable element is obtained directly, which eliminates the need for traversal and search, and does not require locking resource. A lock-free linked list is a linked list that uses atomic operations to optimize the producer-consumer model. I tested the time-consuming comparison of this function under multiple connections based on redis-benchmark (test in smc loopback-ism mode): The function 'smc_buf_get_slot' takes less time when a new SMC link is established: 1. 5us->100ns (when there are 200 active links); 2. 30us->100ns (when there are 1000 active links). Test data with wrk+nginx command: On server: smc_run nginx On client: smc_run wrk -t <2~64> -c 200 -H "Connection: close" http://127.0.0.1 Requests/sec --------+---------------+---------------+ req/s | without patch | apply patch | --------+---------------+---------------+ -t 2 |6924.18 |7456.54 | --------+---------------+---------------+ -t 4 |8731.68 |9660.33 | --------+---------------+---------------+ -t 8 |11363.22 |13802.08 | --------+---------------+---------------+ -t 16 |12040.12 |18666.69 | --------+---------------+---------------+ -t 32 |11460.82 |17017.28 | --------+---------------+---------------+ -t 64 |11018.65 |14974.80 | --------+---------------+---------------+ Transfer/sec --------+---------------+---------------+ trans/s | without patch | apply patch | --------+---------------+---------------+ -t 2 |24.72MB |26.62MB | --------+---------------+---------------+ -t 4 |31.18MB |34.49MB | --------+---------------+---------------+ -t 8 |40.57MB |49.28MB | --------+---------------+---------------+ -t 16 |42.99MB |66.65MB | --------+---------------+---------------+ -t 32 |40.92MB |60.76MB | --------+---------------+---------------+ -t 64 |39.34MB |53.47MB | --------+---------------+---------------+ Signed-off-by: liqiang <liqiang64@xxxxxxxxxx> --- v2: - Correct the acquisition logic of a lock-less linked list.(Dust.Li) - fix comment symbol '//' -> '/**/'.(Dust.Li) v1: https://lore.kernel.org/all/20241101082342.1254-1-liqiang64@xxxxxxxxxx/ net/smc/smc_core.c | 58 ++++++++++++++++++++++++++++++---------------- net/smc/smc_core.h | 4 ++++ 2 files changed, 42 insertions(+), 20 deletions(-) diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c index 500952c2e67b..6f26e70c7c4d 100644 --- a/net/smc/smc_core.c +++ b/net/smc/smc_core.c @@ -16,6 +16,7 @@ #include <linux/wait.h> #include <linux/reboot.h> #include <linux/mutex.h> +#include <linux/llist.h> #include <linux/list.h> #include <linux/smc.h> #include <net/tcp.h> @@ -909,6 +910,8 @@ static int smc_lgr_create(struct smc_sock *smc, struct smc_init_info *ini) for (i = 0; i < SMC_RMBE_SIZES; i++) { INIT_LIST_HEAD(&lgr->sndbufs[i]); INIT_LIST_HEAD(&lgr->rmbs[i]); + init_llist_head(&lgr->rmbs_free[i]); + init_llist_head(&lgr->sndbufs_free[i]); } lgr->next_link_id = 0; smc_lgr_list.num += SMC_LGR_NUM_INCR; @@ -1183,6 +1186,10 @@ static void smcr_buf_unuse(struct smc_buf_desc *buf_desc, bool is_rmb, /* memzero_explicit provides potential memory barrier semantics */ memzero_explicit(buf_desc->cpu_addr, buf_desc->len); WRITE_ONCE(buf_desc->used, 0); + if (is_rmb) + llist_add(&buf_desc->llist, &lgr->rmbs_free[buf_desc->bufsiz_comp]); + else + llist_add(&buf_desc->llist, &lgr->sndbufs_free[buf_desc->bufsiz_comp]); } } @@ -1214,6 +1221,8 @@ static void smc_buf_unuse(struct smc_connection *conn, } else { memzero_explicit(conn->sndbuf_desc->cpu_addr, bufsize); WRITE_ONCE(conn->sndbuf_desc->used, 0); + llist_add(&conn->sndbuf_desc->llist, + &lgr->sndbufs_free[conn->sndbuf_desc->bufsiz_comp]); } SMC_STAT_RMB_SIZE(smc, is_smcd, false, false, bufsize); } @@ -1225,6 +1234,8 @@ static void smc_buf_unuse(struct smc_connection *conn, bufsize += sizeof(struct smcd_cdc_msg); memzero_explicit(conn->rmb_desc->cpu_addr, bufsize); WRITE_ONCE(conn->rmb_desc->used, 0); + llist_add(&conn->rmb_desc->llist, + &lgr->rmbs_free[conn->rmb_desc->bufsiz_comp]); } SMC_STAT_RMB_SIZE(smc, is_smcd, true, false, bufsize); } @@ -1413,13 +1424,21 @@ static void __smc_lgr_free_bufs(struct smc_link_group *lgr, bool is_rmb) { struct smc_buf_desc *buf_desc, *bf_desc; struct list_head *buf_list; + struct llist_head *buf_llist; int i; for (i = 0; i < SMC_RMBE_SIZES; i++) { - if (is_rmb) + if (is_rmb) { buf_list = &lgr->rmbs[i]; - else + buf_llist = &lgr->rmbs_free[i]; + } else { buf_list = &lgr->sndbufs[i]; + buf_llist = &lgr->sndbufs_free[i]; + } + /* just invalid this list first, and then free the memory + * in the following loop + */ + llist_del_all(buf_llist); list_for_each_entry_safe(buf_desc, bf_desc, buf_list, list) { smc_lgr_buf_list_del(lgr, is_rmb, buf_desc); @@ -2087,24 +2106,19 @@ int smc_uncompress_bufsize(u8 compressed) return (int)size; } -/* try to reuse a sndbuf or rmb description slot for a certain - * buffer size; if not available, return NULL - */ -static struct smc_buf_desc *smc_buf_get_slot(int compressed_bufsize, - struct rw_semaphore *lock, - struct list_head *buf_list) +/* use lock less list to save and find reuse buf desc */ +static struct smc_buf_desc *smc_buf_get_slot_free(struct llist_head *buf_llist) { - struct smc_buf_desc *buf_slot; + struct smc_buf_desc *buf_free; + struct llist_node *llnode; - down_read(lock); - list_for_each_entry(buf_slot, buf_list, list) { - if (cmpxchg(&buf_slot->used, 0, 1) == 0) { - up_read(lock); - return buf_slot; - } - } - up_read(lock); - return NULL; + /* lock-less link list don't need an lock */ + llnode = llist_del_first(buf_llist); + if (!llnode) + return NULL; + buf_free = llist_entry(llnode, struct smc_buf_desc, llist); + WRITE_ONCE(buf_free->used, 1); + return buf_free; } /* one of the conditions for announcing a receiver's current window size is @@ -2409,6 +2423,7 @@ static int __smc_buf_create(struct smc_sock *smc, bool is_smcd, bool is_rmb) struct smc_connection *conn = &smc->conn; struct smc_link_group *lgr = conn->lgr; struct list_head *buf_list; + struct llist_head *buf_llist; int bufsize, bufsize_comp; struct rw_semaphore *lock; /* lock buffer list */ bool is_dgraded = false; @@ -2424,15 +2439,17 @@ static int __smc_buf_create(struct smc_sock *smc, bool is_smcd, bool is_rmb) bufsize_comp >= 0; bufsize_comp--) { if (is_rmb) { lock = &lgr->rmbs_lock; + buf_llist = &lgr->rmbs_free[bufsize_comp]; buf_list = &lgr->rmbs[bufsize_comp]; } else { lock = &lgr->sndbufs_lock; + buf_llist = &lgr->sndbufs_free[bufsize_comp]; buf_list = &lgr->sndbufs[bufsize_comp]; } bufsize = smc_uncompress_bufsize(bufsize_comp); /* check for reusable slot in the link group */ - buf_desc = smc_buf_get_slot(bufsize_comp, lock, buf_list); + buf_desc = smc_buf_get_slot_free(buf_llist); if (buf_desc) { buf_desc->is_dma_need_sync = 0; SMC_STAT_RMB_SIZE(smc, is_smcd, is_rmb, true, bufsize); @@ -2457,7 +2474,8 @@ static int __smc_buf_create(struct smc_sock *smc, bool is_smcd, bool is_rmb) SMC_STAT_RMB_ALLOC(smc, is_smcd, is_rmb); SMC_STAT_RMB_SIZE(smc, is_smcd, is_rmb, true, bufsize); - buf_desc->used = 1; + WRITE_ONCE(buf_desc->used, 1); + WRITE_ONCE(buf_desc->bufsiz_comp, bufsize_comp); down_write(lock); smc_lgr_buf_list_add(lgr, is_rmb, buf_list, buf_desc); up_write(lock); diff --git a/net/smc/smc_core.h b/net/smc/smc_core.h index 69b54ecd6503..076ee15f5c10 100644 --- a/net/smc/smc_core.h +++ b/net/smc/smc_core.h @@ -188,10 +188,12 @@ struct smc_link { /* tx/rx buffer list element for sndbufs list and rmbs list of a lgr */ struct smc_buf_desc { struct list_head list; + struct llist_node llist; void *cpu_addr; /* virtual address of buffer */ struct page *pages; int len; /* length of buffer */ u32 used; /* currently used / unused */ + int bufsiz_comp; union { struct { /* SMC-R */ struct sg_table sgt[SMC_LINKS_PER_LGR_MAX]; @@ -278,8 +280,10 @@ struct smc_link_group { unsigned short vlan_id; /* vlan id of link group */ struct list_head sndbufs[SMC_RMBE_SIZES];/* tx buffers */ + struct llist_head sndbufs_free[SMC_RMBE_SIZES]; /* tx buffer free list */ struct rw_semaphore sndbufs_lock; /* protects tx buffers */ struct list_head rmbs[SMC_RMBE_SIZES]; /* rx buffers */ + struct llist_head rmbs_free[SMC_RMBE_SIZES]; /* rx buffer free list */ struct rw_semaphore rmbs_lock; /* protects rx buffers */ u64 alloc_sndbufs; /* stats of tx buffers */ u64 alloc_rmbs; /* stats of rx buffers */ -- 2.43.0
