* Re: [Flent-users] [tohojo/flent] flent on newer versions of Linux (#157)
[not found] <tohojo/flent/issues/157@github.com>
@ 2018-12-31 20:31 ` Toke Høiland-Jørgensen
2019-01-08 11:10 ` Toke Høiland-Jørgensen
2019-01-09 11:51 ` Toke Høiland-Jørgensen
2 siblings, 0 replies; 3+ messages in thread
From: Toke Høiland-Jørgensen @ 2018-12-31 20:31 UTC (permalink / raw)
To: tohojo/flent; +Cc: Subscribed
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Leslie Monis <notifications@github.com> writes:
> Hi,
>
> I have encountered an issue when running the tcp_nup tests on newer
> versions of Linux, specifically v4.16 and up. It seems that flent
> isn't able to get enough data points (for upload throughput) for
> individual TCP flows. This is causing the median TCP upload sum value
> to be way lower than the the average TCP upload sum on a setup with a
> bottleneck bandwidth of 10 Mbits/s. Whereas, the same setup, with
> flent running on a slightly older version of Linux (v4.13 and v4.15)
> gives results with good number of data points for individual TCP
> flows.
Can you supply a debug log file (-L to Flent) and the data file being
produced when you run into this issue?
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^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [Flent-users] [tohojo/flent] flent on newer versions of Linux (#157)
[not found] <tohojo/flent/issues/157@github.com>
2018-12-31 20:31 ` [Flent-users] [tohojo/flent] flent on newer versions of Linux (#157) Toke Høiland-Jørgensen
@ 2019-01-08 11:10 ` Toke Høiland-Jørgensen
2019-01-09 11:51 ` Toke Høiland-Jørgensen
2 siblings, 0 replies; 3+ messages in thread
From: Toke Høiland-Jørgensen @ 2019-01-08 11:10 UTC (permalink / raw)
To: tohojo/flent; +Cc: Subscribed
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Hmm, I think this could be caused by this commit:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0a6b2a1dc2a2105f178255fe495eb914b09cb37a
...which makes TCP always use GSO.
This was introduced in Linux 4.17; is there any chance you could test that the difference appeared in that version?
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^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [Flent-users] [tohojo/flent] flent on newer versions of Linux (#157)
[not found] <tohojo/flent/issues/157@github.com>
2018-12-31 20:31 ` [Flent-users] [tohojo/flent] flent on newer versions of Linux (#157) Toke Høiland-Jørgensen
2019-01-08 11:10 ` Toke Høiland-Jørgensen
@ 2019-01-09 11:51 ` Toke Høiland-Jørgensen
2 siblings, 0 replies; 3+ messages in thread
From: Toke Høiland-Jørgensen @ 2019-01-09 11:51 UTC (permalink / raw)
To: tohojo/flent; +Cc: Subscribed
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Leslie Monis <notifications@github.com> writes:
>> Hmm, I think this could be caused by this commit:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0a6b2a1dc2a2105f178255fe495eb914b09cb37a
>>
>>...which makes TCP always use GSO.
>
> Yes, the commit does seem to cause the issue.
Great, thanks for confirming! Now, the question is what can be done
about it; I'll poke around a bit and see if I can come up with a
workaround.
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