The 05/25/2023 14:34, Haiyang Zhang wrote: > > > -----Original Message----- > > From: Horatiu Vultur <horatiu.vultur@xxxxxxxxxxxxx> > > Sent: Thursday, May 25, 2023 2:49 AM > > To: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx> > > Cc: linux-hyperv@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; Dexuan Cui > > <decui@xxxxxxxxxxxxx>; KY Srinivasan <kys@xxxxxxxxxxxxx>; Paul Rosswurm > > <paulros@xxxxxxxxxxxxx>; olaf@xxxxxxxxx; vkuznets@xxxxxxxxxx; > > davem@xxxxxxxxxxxxx; wei.liu@xxxxxxxxxx; edumazet@xxxxxxxxxx; > > kuba@xxxxxxxxxx; pabeni@xxxxxxxxxx; leon@xxxxxxxxxx; Long Li > > <longli@xxxxxxxxxxxxx>; ssengar@xxxxxxxxxxxxxxxxxxx; linux- > > rdma@xxxxxxxxxxxxxxx; daniel@xxxxxxxxxxxxx; john.fastabend@xxxxxxxxx; > > bpf@xxxxxxxxxxxxxxx; ast@xxxxxxxxxx; Ajay Sharma > > <sharmaajay@xxxxxxxxxxxxx>; hawk@xxxxxxxxxx; linux- > > kernel@xxxxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx > > Subject: Re: [PATCH net] net: mana: Fix perf regression: remove rx_cqes, > > tx_cqes counters > > > > [Some people who received this message don't often get email from > > horatiu.vultur@xxxxxxxxxxxxx. Learn why this is important at > > https://aka.ms/LearnAboutSenderIdentification ] > > > > The 05/24/2023 14:22, Haiyang Zhang wrote: > > > > Hi Haiyang, > > > > > > > > The apc->eth_stats.rx_cqes is one per NIC (vport), and it's on the > > > frequent and parallel code path of all queues. So, r/w into this > > > single shared variable by many threads on different CPUs creates a > > > lot caching and memory overhead, hence perf regression. And, it's > > > not accurate due to the high volume concurrent r/w. > > > > Do you have any numbers to show the improvement of this change? > > The numbers are not published. The perf regression of the previous > patch is very significant, and this patch eliminates the regression. > > > > > > > > > Since the error path of mana_poll_rx_cq() already has warnings, so > > > keeping the counter and convert it to a per-queue variable is not > > > necessary. So, just remove this counter from this high frequency > > > code path. > > > > > > Also, remove the tx_cqes counter for the same reason. We have > > > warnings & other counters for errors on that path, and don't need > > > to count every normal cqe processing. > > > > Will you not have problems with the counter 'apc->eth_stats.tx_cqe_err'? > > It is not in the hot path but you will have concurrent access to it. > > Yes, but that error happens rarely, so a shared variable is good enough. So, I > don't change it in this patch. OK, I understand. Maybe this can be fixed in a different patch at a later point. Thanks. Reviwed-by: Horatiu Vultur <horatiu.vultur@xxxxxxxxxxxxx> > > Thanks, > - Haiyang > -- /Horatiu
