linux-kernel - Re: ????: [PATCH 34/50] sched: numa: Do not trap hinting faults for shared libraries

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Date:	Tue, 17 Sep 2013 09:05:02 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	?????? <ZhangTianFei@...dcoretech.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Rik van Riel <riel@...hat.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...nel.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: ????: [PATCH 34/50] sched: numa: Do not trap hinting faults for
 shared libraries

On Tue, Sep 17, 2013 at 10:02:22AM +0800, ?????? wrote:
> index fd724bc..5d244d0 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -1227,6 +1227,16 @@ void task_numa_work(struct callback_head *work)
>  		if (!vma_migratable(vma))
>  			continue;
>  
> +		/*
> +		 * Shared library pages mapped by multiple processes are not
> +		 * migrated as it is expected they are cache replicated. Avoid
> +		 * hinting faults in read-only file-backed mappings or the vdso
> +		 * as migrating the pages will be of marginal benefit.
> +		 */
> +		if (!vma->vm_mm ||
> +		    (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
> +			continue;
> +
>  
> =?? May I ask a question, we should consider some VMAs canot be scaned for BalanceNuma?
> (VM_DONTEXPAND | VM_RESERVED | VM_INSERTPAGE |
> 				  VM_NONLINEAR | VM_MIXEDMAP | VM_SAO));

vma_migratable check covers most of the other VMAs we do not care
about.  I do not see the point of checking for some of the VMA flags you
mention. Please state which of the additional flags that you think should
be checked and why.

-- 
Mel Gorman
SUSE Labs
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