linux-kernel - Re: [PATCH 3/8] Add a PF flag for ksoftirqd identification

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Date:	Fri, 15 Oct 2010 16:46:28 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Venkatesh Pallipadi <venki@...gle.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	linux-kernel@...r.kernel.org, Paul Turner <pjt@...gle.com>
Subject: Re: [PATCH 3/8] Add a PF flag for ksoftirqd identification

Le lundi 04 octobre 2010 à 17:03 -0700, Venkatesh Pallipadi a écrit :
> To account softirq time cleanly in scheduler, we need to identify whether
> softirq is invoked in ksoftirqd context or softirq at hardirq tail context.
> Add PF_KSOFTIRQD for that purpose.
> 
> As all PF flag bits are currently taken, create space by moving one of the
> infrequently used bits (PF_THREAD_BOUND) down in task_struct to be along
> with some other state fields.
> 
> Signed-off-by: Venkatesh Pallipadi <venki@...gle.com>

Instead of using one bit per task (and fight to find a free bit) why not
using existing :

DEFINE_PER_CPU(struct task_struct *, ksoftirqd);

And check if current is ksoftirqd ?

if (__get_cpu_var(ksoftirqd) == current) ...


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