"Thomas Rosenstein" <[email protected]> writes:
> On 5 Nov 2020, at 12:21, Toke Høiland-Jørgensen wrote: > >> "Thomas Rosenstein" <[email protected]> writes: >> >>>> If so, this sounds more like a driver issue, or maybe something to >>>> do >>>> with scheduling. Does it only happen with ICMP? You could try this >>>> tool >>>> for a userspace UDP measurement: >>> >>> It happens with all packets, therefore the transfer to backblaze with >>> 40 >>> threads goes down to ~8MB/s instead of >60MB/s >> >> Huh, right, definitely sounds like a kernel bug; or maybe the new >> kernel >> is getting the hardware into a state where it bugs out when there are >> lots of flows or something. >> >> You could try looking at the ethtool stats (ethtool -S) while running >> the test and see if any error counters go up. Here's a handy script to >> monitor changes in the counters: >> >> https://github.com/netoptimizer/network-testing/blob/master/bin/ethtool_stats.pl >> >>> I'll try what that reports! >>> >>>> Also, what happens if you ping a host on the internet (*through* the >>>> router instead of *to* it)? >>> >>> Same issue, but twice pronounced, as it seems all interfaces are >>> affected. >>> So, ping on one interface and the second has the issue. >>> Also all traffic across the host has the issue, but on both sides, so >>> ping to the internet increased by 2x >> >> Right, so even an unloaded interface suffers? But this is the same >> NIC, >> right? So it could still be a hardware issue... >> >>> Yep default that CentOS ships, I just tested 4.12.5 there the issue >>> also >>> does not happen. So I guess I can bisect it then...(really don't want >>> to >>> 😃) >> >> Well that at least narrows it down :) > > I just tested 5.9.4 seems to also fix it partly, I have long stretches > where it looks good, and then some increases again. (3.10 Stock has them > too, but not so high, rather 1-3 ms) > > for example: > > 64 bytes from x.x.x.x: icmp_seq=10 ttl=64 time=0.169 ms > 64 bytes from x.x.x.x: icmp_seq=11 ttl=64 time=5.53 ms > 64 bytes from x.x.x.x: icmp_seq=12 ttl=64 time=9.44 ms > 64 bytes from x.x.x.x: icmp_seq=13 ttl=64 time=0.167 ms > 64 bytes from x.x.x.x: icmp_seq=14 ttl=64 time=3.88 ms > > and then again: > > 64 bytes from x.x.x.x: icmp_seq=15 ttl=64 time=0.569 ms > 64 bytes from x.x.x.x: icmp_seq=16 ttl=64 time=0.148 ms > 64 bytes from x.x.x.x: icmp_seq=17 ttl=64 time=0.286 ms > 64 bytes from x.x.x.x: icmp_seq=18 ttl=64 time=0.257 ms > 64 bytes from x.x.x.x: icmp_seq=19 ttl=64 time=0.220 ms > 64 bytes from x.x.x.x: icmp_seq=20 ttl=64 time=0.125 ms > 64 bytes from x.x.x.x: icmp_seq=21 ttl=64 time=0.188 ms > 64 bytes from x.x.x.x: icmp_seq=22 ttl=64 time=0.202 ms > 64 bytes from x.x.x.x: icmp_seq=23 ttl=64 time=0.195 ms > 64 bytes from x.x.x.x: icmp_seq=24 ttl=64 time=0.177 ms > 64 bytes from x.x.x.x: icmp_seq=25 ttl=64 time=0.242 ms > 64 bytes from x.x.x.x: icmp_seq=26 ttl=64 time=0.339 ms > 64 bytes from x.x.x.x: icmp_seq=27 ttl=64 time=0.183 ms > 64 bytes from x.x.x.x: icmp_seq=28 ttl=64 time=0.221 ms > 64 bytes from x.x.x.x: icmp_seq=29 ttl=64 time=0.317 ms > 64 bytes from x.x.x.x: icmp_seq=30 ttl=64 time=0.210 ms > 64 bytes from x.x.x.x: icmp_seq=31 ttl=64 time=0.242 ms > 64 bytes from x.x.x.x: icmp_seq=32 ttl=64 time=0.127 ms > 64 bytes from x.x.x.x: icmp_seq=33 ttl=64 time=0.217 ms > 64 bytes from x.x.x.x: icmp_seq=34 ttl=64 time=0.184 ms > > > For me it looks now that there was some fix between 5.4.60 and 5.9.4 ... > anyone can pinpoint it? $ git log --no-merges --oneline v5.4.60..v5.9.4|wc -l 72932 Only 73k commits; should be easy, right? :) (In other words no, I have no idea; I'd suggest either (a) asking on netdev, (b) bisecting or (c) using 5.9+ and just making peace with not knowing). >>>> How did you configure the new kernel? Did you start from scratch, or >>>> is >>>> it based on the old centos config? >>> >>> first oldconfig and from there then added additional options for IB, >>> NVMe, etc (which I don't really need on the routers) >> >> OK, so you're probably building with roughly the same options in terms >> of scheduling granularity etc. That's good. Did you enable spectre >> mitigations etc on the new kernel? What's the output of >> `tail /sys/devices/system/cpu/vulnerabilities/*` ? > > mitigations are off Right, I just figured maybe you were hitting some threshold that involved a lot of indirect calls which slowed things down due to mitigations. Guess not, then... -Toke _______________________________________________ Bloat mailing list [email protected] https://lists.bufferbloat.net/listinfo/bloat
