linux-kernel - Re: [PATCH] net: use __GFP_NORETRY for high order allocations

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Message-ID: <alpine.DEB.2.02.1402061335280.12761@chino.kir.corp.google.com>
Date:	Thu, 6 Feb 2014 13:39:01 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Joe Perches <joe@...ches.com>
cc:	Eric Dumazet <eric.dumazet@...il.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net: use __GFP_NORETRY for high order allocations

On Thu, 6 Feb 2014, Joe Perches wrote:

> > If they absolutely require local memory to 
> > currnet's cpu node then that would make sense,
> 
> I presumed THISNODE would be used only with NORETRY
> 

Unfortunately, that would avoid attempting to defragment or reclaim 
remotely for the order-3 allocation and only allocate remotely for 
order-0.

So we have to make a decision here what is more important: allocating 
high-order memory or local memory to current's cpu at this given time?

The policy of transparent hugepages, for example, is always to allocate 
order-9 memory remotely instead of falling back to allocating a smallpage 
locally.

The original code never cared about local vs remote memory, so I don't 
think there's any restriction to allocating remotely.  I also don't know 
many allocators that do __GFP_THISNODE and care about local memory to 
current's cpu at this point in time, usually users of that flag are 
allocating memory that must be local to a specific node (for things like 
kmem_cache_alloc_node()).
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