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Date: Tue, 14 Jul 2009 14:30:28 -0700
Message-ID: <2f86c2480907141430u314f8987s857bdaa229d6e482@mail.gmail.com>
Subject: Re: [PATCH 3/3] Quick vmalloc vs kmalloc fix to the case where array 
	size is too large
From: Benjamin Blum <bblum@google.com>
To: Paul Menage <menage@google.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
       akpm@linux-foundation.org
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Indeed.

Alternatively, I could make it case on KMALLOC_MAX_SIZE as follows:

if (size > KMALLOC_MAX_SIZE) {
    /* use vmalloc directly */
} else {
    /* try kmalloc, and, expecting fragmentation, if that fails, use vmalloc */
}

As the free wrapper uses is_vmalloc_addr, it'd work fine and be able
to decide for a certain range of sizes whether kmalloc or vmalloc is
appropriate.

On Tue, Jul 14, 2009 at 10:50 AM, Paul Menage<menage@google.com> wrote:
> On Tue, Jul 14, 2009 at 10:47 AM, Dave Hansen<dave@linux.vnet.ibm.com> wrote:
>>
>> How big were those allocations that were failing? ?The code made it
>> appear that order-2 (PAGE_SIZE*4) allocations were failing. ?That's a
>> bit lower than I'd expect the page allocator to start failing.
>
> I think it depends on how much fragmentation you've got.
>
> We've seen it fail for cpusets with (I guess) hundreds or thousands of threads.
>
> Paul
>
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