linux-kernel - Re: [RFC PATCH] sched&net: avoid over-pulling tasks due to network interrupts

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Date:   Fri, 5 Nov 2021 13:24:02 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Barry Song <21cnbao@...il.com>
Cc:     davem@...emloft.net, kuba@...nel.org, edumazet@...gle.com,
        pabeni@...hat.com, fw@...len.de, mingo@...hat.com,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, tglx@...utronix.de,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linuxarm@...wei.com, guodong.xu@...aro.org, yangyicong@...wei.com,
        shenyang39@...wei.com, tangchengchang@...wei.com,
        Barry Song <song.bao.hua@...ilicon.com>,
        Libo Chen <libo.chen@...cle.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>
Subject: Re: [RFC PATCH] sched&net: avoid over-pulling tasks due to network
 interrupts

On Fri, Nov 05, 2021 at 06:51:36PM +0800, Barry Song wrote:
> From: Barry Song <song.bao.hua@...ilicon.com>
> 
> In LPC2021, both Libo Chen and Tim Chen have reported the overpull
> of network interrupts[1]. For example, while running one database,
> ethernet is located in numa0, numa1 might be almost idle due to
> interrupts are pulling tasks to numa0 because of wake_up affine.
> I have seen the same problem. One way to solve this problem is
> moving to a normal wakeup in network rather than using a sync
> wakeup which will be more aggressively pulling tasks in scheduler
> core.
> 
> On kunpeng920 with 4numa, ethernet is located at numa0, storage
> disk is located at numa2. While using sysbench to connect this
> mysql machine, I am seeing numa1 is idle though numa0,2 and 3
> are quite busy.
> 

> I am not saying this patch is exactly the right approach, But I'd
> like to use this RFC to connect the people of net and scheduler,
> and start the discussion in this wider range.

Well the normal way would be to use multi-queue crud and/or receive
packet steering to get the interrupt/wakeup back to the cpu that data
came from.