Jakub Kicinski wrote:
On Tue, 14 May 2024 14:13:21 +0200 Geert Uytterhoeven wrote:
On Thu, May 9, 2024 at 9:09 PM Richard Gobert richardbgobert@gmail.com wrote:
{inet,ipv6}_gro_receive functions perform flush checks (ttl, flags, iph->id, ...) against all packets in a loop. These flush checks are used in all merging UDP and TCP flows.
These checks need to be done only once and only against the found p skb, since they only affect flush and not same_flow.
This patch leverages correct network header offsets from the cb for both outer and inner network headers - allowing these checks to be done only once, in tcp_gro_receive and udp_gro_receive_segment. As a result, NAPI_GRO_CB(p)->flush is not used at all. In addition, flush_id checks are more declarative and contained in inet_gro_flush, thus removing the need for flush_id in napi_gro_cb.
This results in less parsing code for non-loop flush tests for TCP and UDP flows.
To make sure results are not within noise range - I've made netfilter drop all TCP packets, and measured CPU performance in GRO (in this case GRO is responsible for about 50% of the CPU utilization).
perf top while replaying 64 parallel IP/TCP streams merging in GRO: (gro_receive_network_flush is compiled inline to tcp_gro_receive) net-next: 6.94% [kernel] [k] inet_gro_receive 3.02% [kernel] [k] tcp_gro_receive
patch applied: 4.27% [kernel] [k] tcp_gro_receive 4.22% [kernel] [k] inet_gro_receive
perf top while replaying 64 parallel IP/IP/TCP streams merging in GRO (same results for any encapsulation, in this case inet_gro_receive is top offender in net-next) net-next: 10.09% [kernel] [k] inet_gro_receive 2.08% [kernel] [k] tcp_gro_receive
patch applied: 6.97% [kernel] [k] inet_gro_receive 3.68% [kernel] [k] tcp_gro_receive
Signed-off-by: Richard Gobert richardbgobert@gmail.com
Thanks for your patch, which is now commit 4b0ebbca3e167976 ("net: gro: move L3 flush checks to tcp_gro_receive and udp_gro_receive_segment") in net-next/main (next-20240514).
noreply@ellerman.id.au reports build failures on m68k, e.g. http://kisskb.ellerman.id.au/kisskb/buildresult/15168903/
net/core/gro.c: In function ‘dev_gro_receive’: ././include/linux/compiler_types.h:460:38: error: call to‘__compiletime_assert_654’ declared with attribute error: BUILD_BUG_ON failed: !IS_ALIGNED(offsetof(struct napi_gro_cb, zeroed), sizeof(u32))
Hi Richard, any chance of getting this fixed within the next 2 hours? I can't send the net-next PR if it doesn't build on one of the arches..
Hi Jakub and Geert, I'm only seeing this mail now, sorry for the late response. I can fix this within the next two hours, would you prefer a standalone patch or should I add it to this patch series?