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Message-ID: <20230227152741.4a53634b@kernel.org> Date: Mon, 27 Feb 2023 15:27:41 -0800 From: Jakub Kicinski <kuba@...nel.org> To: edumazet@...gle.com Cc: Florian Westphal <fw@...len.de>, netdev@...r.kernel.org, davem@...emloft.net, pabeni@...hat.com, shakeelb@...gle.com, soheil@...gle.com Subject: Re: [PATCH net] net: avoid indirect memory pressure calls On Fri, 24 Feb 2023 19:46:06 +0100 Florian Westphal wrote: > There is a noticeable tcp performance regression (loopback or cross-netns), > seen with iperf3 -Z (sendfile mode) when generic retpolines are needed. > > With SK_RECLAIM_THRESHOLD checks gone number of calls to enter/leave > memory pressure happen much more often. For TCP indirect calls are > used. > > We can't remove the if-set-return short-circuit check in > tcp_enter_memory_pressure because there are callers other than > sk_enter_memory_pressure. Doing a check in the sk wrapper too > reduces the indirect calls enough to recover some performance. > > Before, > 0.00-60.00 sec 322 GBytes 46.1 Gbits/sec receiver > > After: > 0.00-60.04 sec 359 GBytes 51.4 Gbits/sec receiver > > "iperf3 -c $peer -t 60 -Z -f g", connected via veth in another netns. > > Fixes: 4890b686f408 ("net: keep sk->sk_forward_alloc as small as possible") > Signed-off-by: Florian Westphal <fw@...len.de> Looks acceptable, Eric?
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