Re: [RFC][PATCH] Manage jbd allocations from its own slabs

Christoph Hellwig <[email protected]> Thu, 24 Aug 2006 19:53:42 +0100
Newsgroups gmane.comp.file-systems.ext2.devel,gmane.linux.kernel
Message-ID <[email protected]>
On Wed, Aug 23, 2006 at 04:08:15PM -0700, Badari Pulavarty wrote:
> Hi,
> 
> Here is the fix to "bh: Ensure bh fits within a page" problem
> caused by JBD.
> 
> BTW, I realized that this problem can happen only with 1k, 2k
> filesystems - as 4k, 8k allocations disable slab debug 
> automatically. But for completeness, I created slabs for those
> also.
> 
> What do you think ? I ran basic tests and things are fine.

Why can't you just use alloc_page?  I bet the whole slab overhead
eats more memory than what's wasted when using alloc_pages.  Especially
as the typical usecase is a 4k blocks filesystem with 4k pagesize
where the overhead of alloc_page is non-existant.

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