linux-kernel - Re: [PATCH 0/7] Kill PF

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Message-ID: <alpine.DEB.2.00.0911170034500.22639@chino.kir.corp.google.com>
Date:	Tue, 17 Nov 2009 00:36:38 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
cc:	linux-mm <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 0/7] Kill PF_MEMALLOC abuse

On Tue, 17 Nov 2009, KOSAKI Motohiro wrote:

> > I agree in principle with removing non-VM users of PF_MEMALLOC, but I 
> > think it should be left to the individual subsystem maintainers to apply 
> > or ack since the allocations may depend on the __GFP_NORETRY | ~__GFP_WAIT 
> > behavior of PF_MEMALLOC.  This could be potentially dangerous for a 
> > PF_MEMALLOC user if allocations made by the kthread, for example, should 
> > never retry for orders smaller than PAGE_ALLOC_COSTLY_ORDER or block on 
> > direct reclaim.
> 
> if there is so such reason. we might need to implement another MM trick.
> but keeping this strage usage is not a option. All memory freeing activity
> (e.g. page out, task killing) need some memory. we need to protect its
> emergency memory. otherwise linux reliability decrease dramatically when
> the system face to memory stress.
> 

Right, that's why I agree with trying to remove non-VM use of PF_MEMALLOC, 
but I think this patchset needs to go through the individual subsystem 
maintainers so they can ensure the conversion doesn't cause undesirable 
results if their kthreads' memory allocations depend on the __GFP_NORETRY 
behavior that PF_MEMALLOC ensures.  Otherwise it looks good.
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