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Date: Sat, 15 Nov 2008 21:03:34 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Arjan van de Ven <arjan@infradead.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>, Paul Menage <menage@google.com>,
       kamezawa.hiroyu@jp.fujitsu.com,
       Balbir Singh <balbir@linux.vnet.ibm.com>,
       Jens Axboe <jens.axboe@oracle.com>,
       "David S. Miller" <davem@davemloft.net>, Jan Kara <jack@suse.cz>,
       Jes Sorensen <jes@sgi.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/7] mm: introduce simple_malloc()/simple_free()
Message-Id: <20081115210334.3870cdf6.akpm@linux-foundation.org>
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On Sat, 15 Nov 2008 20:52:29 -0800 Arjan van de Ven <arjan@infradead.org> wrote:

> On Sun, 16 Nov 2008 12:33:15 +0800
> Lai Jiangshan <laijs@cn.fujitsu.com> wrote:
> 
> > 
> > some subsystem needs vmalloc() when required memory is large.
> > but current kernel has not APIs for this requirement.
> > this patch introduces simple_malloc() and simple_free().
> 
> Hi
> 
> I kinda really don't like this approach. vmalloc() (and especially,
> vfree()) is a really expensive operation, and vmalloc()'d memory is
> also slower (due to tlb pressure).

And it can fragment, which effectively means a dead box.

> Realistically, people should try hard
> to use small datastructure instead....

Yup, it makes it easier for people to do something which we strongly
discourage.  The risk got worse with all these 64-bit machines with
vast amounts of virtual address space.  It makes it easier for people
to develop and "test" code which isn't reliable on smaller machines.