linux-kernel - Re: [MODSLAB 3/7] A Kmalloc subsystem

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Date:	Sat, 19 Aug 2006 09:08:26 +0200
From:	Manfred Spraul <manfred@...orfullife.com>
To:	Christoph Lameter <clameter@....com>
CC:	Andi Kleen <ak@....de>, mpm@...enic.com,
	Marcelo Tosatti <marcelo@...ck.org>,
	linux-kernel@...r.kernel.org,
	Nick Piggin <nickpiggin@...oo.com.au>, Andi Kleen <ak@...e.de>,
	Dave Chinner <dgc@....com>
Subject: Re: [MODSLAB 3/7] A Kmalloc subsystem

Christoph Lameter wrote:

>>If you have non-power-of-two caches, you could store the control data at
>>(addr&(~PAGE_SIZE)) - the lookup would be much faster. I wrote a patch a few
>>weeks ago, it's attached.
>>    
>>
>
>That would only work for slabs that use order 0 pages.
>
>  
>
Most slabs are order 0. Actually: there are only 6 slabs that are not 
order 0 (excluding the kmalloc caches) on my system.

What about:

if (unlikely(addr & (~(PAGE_SIZE-1))))
    slabp=virt_to_page(addr)->pagefield;
 else
    slabp=addr & (~(PAGE_SIZE-1));

Modify the kmalloc caches slightly and use non-power-of-2 cache sizes. 
Move the kmalloc(PAGE_SIZE) users to gfp.

 From my system:
good order 1 slab caches: (i.e.: forcing them to order 0 wastes some memory)
    biovec-128
    blkdev_queue
    mqueue_inode_cache
    RAWv6
    UDPv6
bogus order 1 caches: (i.e.: they could be order 0 without wasting memory)
    biovec-(256)

--
    Manfred
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