On 2022/1/20 16:24, Leon Romanovsky wrote: > On Thu, Jan 20, 2022 at 02:51:40PM +0800, Guangguan Wang wrote: >> This implement rq flow control in smc-r link layer. QPs >> communicating without rq flow control, in the previous >> version, may result in RNR (reveive not ready) error, which >> means when sq sends a message to the remote qp, but the >> remote qp's rq has no valid rq entities to receive the message. >> In RNR condition, the rdma transport layer may retransmit >> the messages again and again until the rq has any entities, >> which may lower the performance, especially in heavy traffic. >> Using credits to do rq flow control can avoid the occurrence >> of RNR. >> >> Test environment: >> - CPU Intel Xeon Platinum 8 core, mem 32 GiB, nic Mellanox CX4. >> - redis benchmark 6.2.3 and redis server 6.2.3. >> - redis server: redis-server --save "" --appendonly no >> --protected-mode no --io-threads 7 --io-threads-do-reads yes >> - redis client: redis-benchmark -h 192.168.26.36 -q -t set,get >> -P 1 --threads 7 -n 2000000 -c 200 -d 10 >> >> Before: >> SET: 205229.23 requests per second, p50=0.799 msec >> GET: 212278.16 requests per second, p50=0.751 msec >> >> After: >> SET: 623674.69 requests per second, p50=0.303 msec >> GET: 688326.00 requests per second, p50=0.271 msec >> >> The test of redis-benchmark shows that more than 3X rps >> improvement after the implementation of rq flow control. >> >> Signed-off-by: Guangguan Wang <guangguan.wang@xxxxxxxxxxxxxxxxx> >> --- >> net/smc/af_smc.c | 12 ++++++ >> net/smc/smc_cdc.c | 10 ++++- >> net/smc/smc_cdc.h | 3 +- >> net/smc/smc_clc.c | 3 ++ >> net/smc/smc_clc.h | 3 +- >> net/smc/smc_core.h | 17 ++++++++- >> net/smc/smc_ib.c | 6 ++- >> net/smc/smc_llc.c | 92 +++++++++++++++++++++++++++++++++++++++++++++- >> net/smc/smc_llc.h | 5 +++ >> net/smc/smc_wr.c | 30 ++++++++++++--- >> net/smc/smc_wr.h | 54 ++++++++++++++++++++++++++- >> 11 files changed, 222 insertions(+), 13 deletions(-) > > <...> > >> + // set peer rq credits watermark, if less than init_credits * 2/3, >> + // then credit announcement is needed. > > <...> > >> + // set peer rq credits watermark, if less than init_credits * 2/3, >> + // then credit announcement is needed. > > <...> > >> + // credits have already been announced to peer > > <...> > >> + // set local rq credits high watermark to lnk->wr_rx_cnt / 3, >> + // if local rq credits more than high watermark, announcement is needed. > > <...> > >> +// get one tx credit, and peer rq credits dec > > <...> > >> +// put tx credits, when some failures occurred after tx credits got >> +// or receive announce credits msgs >> +static inline void smc_wr_tx_put_credits(struct smc_link *link, int credits, bool wakeup) > > <...> > >> +// to check whether peer rq credits is lower than watermark. >> +static inline int smc_wr_tx_credits_need_announce(struct smc_link *link) > > <...> > >> +// get local rq credits and set credits to zero. >> +// may called when announcing credits >> +static inline int smc_wr_rx_get_credits(struct smc_link *link) > > Please try to use C-style comments. > > Thanks Thanks for your advice, I will modify it in the next version of patch.
