linux-kernel - Re: [PATCH] sched/core: Clear the root_domain cpumasks in init

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Message-ID: <20151203093525.GQ17308@twins.programming.kicks-ass.net>
Date:	Thu, 3 Dec 2015 10:35:25 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Xunlei Pang <xlpang@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] sched/core: Clear the root_domain cpumasks in
 init_rootdomain()

On Thu, Dec 03, 2015 at 10:44:08AM +0800, Xunlei Pang wrote:

> > Nice, will you be looking for similar issues elsewhere in the scheduler
> > too?
> 
> Sure :-)

Thanks!

> >>> in alloc_rootdomain() ?
> >> There is a "memset(rd, 0, sizeof(*rd))" in init_rootdomain(),
> >> so I don't think we need to do this in alloc_rootdomain().
> > Ah, right there is. Which also clears the mask for small systems.
> 
> Yeah, maybe we can improve it using alloc_cpumask_var() with
> __GFP_ZERO instead of zalloc_cpumask_var() to avoid duplicate
> clean for small systems.

This isn't a performance critical path, so clarity and correctness are
more important than performance.
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