Messages in this thread | | | Date | Thu, 24 Aug 2006 12:11:25 -0700 | From | Badari Pulavarty <> | Subject | Re: [RFC][PATCH] Manage jbd allocations from its own slabs |
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Christoph Hellwig wrote: > 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. >
Yes. That was what proposed earlier. But for 1k, 2k allocations we end up wasting whole page. Isn't it ? Thats why I created right sized slabs and disable slab-debug. I guess, I can do this only for 1k, 2k filesystems and directly use alloc_page() for 4k and 8k - but that would make code ugly and also it doesn't handle cases for bigger base pagesize systems (64k power).
Thanks, Badari
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