On 05/09/2018 11:43 AM, Ben Greear wrote: > On 05/08/2018 10:10 AM, Eric Dumazet wrote: >> >> >> On 05/08/2018 09:44 AM, Ben Greear wrote: >>> Hello, >>> >>> I am trying to track down a performance regression that appears to be >>> between 4.13 >>> and 4.14. >>> >>> I first saw the problem with a hacked version of pktgen on some ixgbe NICs. >>> 4.13 can do >>> right at 10G bi-directional on two ports, and 4.14 and later can do only >>> about 6Gbps. >>> >>> I also tried with user-space UDP traffic on a stock kernel, and I can get >>> about 3.2Gbps combined tx+rx >>> on 4.14 and about 4.4Gbps on 4.13. >>> >>> Attempting to bisect seems to be triggering a weirdness in git, and also >>> lots of commits >>> crash or do not bring up networking, which makes the bisect difficult. >>> >>> Looking at perf top, it would appear that some lock is probably to blame. >> >> >> perf record -a -g -e cycles:pp sleep 5 >> perf report >> >> Then you'll be able to tell us which lock (or call graph) is killing your >> perf. >> > > I seem to be chasing multiple issues. For 4.13, at least part of my problem > was that LOCKDEP was enabled, > during my bisect, though it does NOT appear enabled in 4.16. I think maybe > CONFIG_LOCKDEP moved to CONFIG_PROVE_LOCKING > in 4.16, or something like that? My 4.16 .config does have > CONFIG_LOCKDEP_SUPPORT enabled, and I see no option to disable it: > > [greearb@ben-dt3 linux-4.16.x64]$ grep LOCKDEP .config > CONFIG_LOCKDEP_SUPPORT=y > > > For 4.16, I am disabling RETRAMPOLINE...are there any other such things I need > to disable to keep from getting a performance hit from the spectre-related bug > fixes? At this point, I do not care about the security implications. > > greearb@ben-dt3 linux-4.16.x64]$ grep RETPO .config > # CONFIG_RETPOLINE is not set > > > Thanks, > Ben >
No idea really, you mention a 4.13 -> 4.14 regression and jump then to 4.16 :/ Before doing a (painful) dissection, the perf output would immediately tell you if something is really wrong on your .config.
