netdev - Re: Serious performance degradation in Linux 4.15

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Message-ID: <20180210140117.GP25201@hirez.programming.kicks-ass.net>
Date:   Sat, 10 Feb 2018 15:01:17 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Jon Maloy <jon.maloy@...csson.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "David Miller (davem@...emloft.net)" <davem@...emloft.net>
Subject: Re: Serious performance degradation in Linux 4.15

On Fri, Feb 09, 2018 at 05:59:12PM +0000, Jon Maloy wrote:
> The two commits 
> d153b153446f7 (" sched/core: Fix wake_affine() performance regression") and
> f2cdd9cc6c97 ("sched/core: Address more wake_affine() regressions")
> are causing a serious performance degradation in Linux 4.5.
> 
> The effect is worst on TIPC, but even TCP is affected, as the figures below show. 

I did run a whole bunch of netperf and didn't see anything like that.
0-day also didn't report anything, and it too runs netperf.

I'll try and see if I can reproduce somewhere next week.