On Fri, Sep 02, 2022 at 06:02:12AM -0600, Jens Axboe wrote: > On 9/1/22 7:04 PM, Roman Gushchin wrote: > > On Thu, Sep 01, 2022 at 08:17:47PM -0400, Kent Overstreet wrote: > >> On Thu, Sep 01, 2022 at 03:53:57PM -0700, Roman Gushchin wrote: > >>> I'd suggest to run something like iperf on a fast hardware. And maybe some > >>> io_uring stuff too. These are two places which were historically most sensitive > >>> to the (kernel) memory accounting speed. > >> > >> I'm getting wildly inconsistent results with iperf. > >> > >> io_uring-echo-server and rust_echo_bench gets me: > >> Benchmarking: 127.0.0.1:12345 > >> 50 clients, running 512 bytes, 60 sec. > >> > >> Without alloc tagging: 120547 request/sec > >> With: 116748 request/sec > >> > >> https://github.com/frevib/io_uring-echo-server > >> https://github.com/haraldh/rust_echo_bench > >> > >> How's that look to you? Close enough? :) > > > > Yes, this looks good (a bit too good). > > > > I'm not that familiar with io_uring, Jens and Pavel should have a better idea > > what and how to run (I know they've workarounded the kernel memory accounting > > because of the performance in the past, this is why I suspect it might be an > > issue here as well). > > io_uring isn't alloc+free intensive on a per request basis anymore, it > would not be a good benchmark if the goal is to check for regressions in > that area. Good to know. The benchmark is still a TCP benchmark though, so still useful. Matthew suggested while true; do echo 1 >/tmp/foo; rm /tmp/foo; done I ran that on tmpfs, and the numbers with and without alloc tagging were statistically equal - there was a fair amount of variation, it wasn't a super controlled test, anywhere from 38-41 seconds with 100000 iterations (and alloc tagging was some of the faster runs). But with memcg off, it ran in 32-33 seconds. We're piggybacking on the same mechanism memcg uses for stashing per-object pointers, so it looks like that's the bigger cost.
