On 2024-11-02 14:43:52, Li Qiang wrote: > > >在 2024/11/1 18:52, Dust Li 写道: >> On 2024-11-01 16:23:42, liqiang wrote: >>> connections based on redis-benchmark (test in smc loopback-ism mode): >> >> I think you can run test wrk/nginx test with short-lived connection. >> For example: >> >> ``` >> # client >> wrk -H "Connection: close" http://$serverIp >> >> # server >> nginx >> ``` > >I tested with nginx, the test command is: ># server >smc_run nginx > ># client >smc_run wrk -t <2,4,8,16,32,64> -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 | >--------+---------------+---------------+ > >> >>> >>> 1. On the current version: >>> [x.832733] smc_buf_get_slot cost:602 ns, walk 10 buf_descs >>> [x.832860] smc_buf_get_slot cost:329 ns, walk 12 buf_descs >>> [x.832999] smc_buf_get_slot cost:479 ns, walk 17 buf_descs >>> [x.833157] smc_buf_get_slot cost:679 ns, walk 13 buf_descs >>> ... >>> [x.045240] smc_buf_get_slot cost:5528 ns, walk 196 buf_descs >>> [x.045389] smc_buf_get_slot cost:4721 ns, walk 197 buf_descs >>> [x.045537] smc_buf_get_slot cost:4075 ns, walk 198 buf_descs >>> [x.046010] smc_buf_get_slot cost:6476 ns, walk 199 buf_descs >>> >>> 2. Apply this patch: >>> [x.180857] smc_buf_get_slot_free cost:75 ns >>> [x.181001] smc_buf_get_slot_free cost:147 ns >>> [x.181128] smc_buf_get_slot_free cost:97 ns >>> [x.181282] smc_buf_get_slot_free cost:132 ns >>> [x.181451] smc_buf_get_slot_free cost:74 ns >>> >>> It can be seen from the data that it takes about 5~6us to traverse 200 >> >> Based on your data, I'm afraid the short-lived connection >> test won't show much benificial. Since the time to complete a >> SMC-R connection should be several orders of magnitude larger >> than 100ns. > >Sorry, I didn't explain my test data well before. > >The main optimized functions of this patch are as follows: > >``` >struct smc_buf_desc *smc_buf_get_slot(...) >{ > struct smc_buf_desc *buf_slot; > 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; >} >``` >The above data is the time-consuming data of this function. >If the current system has 200 active links, then during the >process of establishing a new SMC connection, this function >must traverse all 200 active links, which will take 5~6us. >If there are already 1,000 for active links, it takes about 30us. > >After optimization, this function takes <100ns, it has nothing >to do with the number of active links. > >Moreover, the lock has been removed, which is firendly to multi-thread >parallel scenarios. > >The optimized code is as follows: > >``` >static struct smc_buf_desc *smc_buf_get_slot_free(struct llist_head *buf_llist) >{ > struct smc_buf_desc *buf_free; > struct llist_node *llnode; > > if (llist_empty(buf_llist)) > return NULL; > // lock-less link list don't need an lock ^^^ kernel use /**/ for comments > llnode = llist_del_first(buf_llist); > buf_free = llist_entry(llnode, struct smc_buf_desc, llist); If 2 CPU both passed the llist_empty() check, only 1 CPU can get llnode, the other one should be NULL ? > WRITE_ONCE(buf_free->used, 1); > return buf_free; >} >``` > >-- >Cheers, >Li Qiang
