linux-kernel - Re: Why ping latency is smaller with shorter send interval?

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Message-ID: <20201002095648.GB3783@1wt.eu>
Date:   Fri, 2 Oct 2020 11:56:48 +0200
From:   Willy Tarreau <w@....eu>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     ??? <muryo.ye@...il.com>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: Why ping latency is smaller with shorter send interval?

On Fri, Oct 02, 2020 at 11:26:00AM +0200, Eric Dumazet wrote:
> 2) Idle cpus can be put in a power conserving state.
>   It takes time to exit from these states, as you noticed.
>   These delays can typically be around 50 usec, or more.

This is often the case in my experience. I'm even used to starting a
busy loop in SCHED_IDLE prio on certain machines or in certain VMs
just to keep them busy, and to see the ping latency cut in half.

Willy