Messages in this thread | | | From | Charles Manning <> | Subject | Trying to use SLUB in an odd way | Date | Mon, 24 May 2010 14:39:48 +1200 |
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Hi
YAFFS uses an internal almost slub-like allocator and I've been looking at moving it to use SLUB as part of an attempt to mainline yaffs.
In yaffs I create a lot of tiny objects which are allocated in blocks, like slub, and then managed in a free list. Very slubbish so far, but mine is far less intelligent than slub.
The difference though is that I can keep the objects for each mount separate and can dump the whole lot on umount without individually freeing objects. I just deallocate my whole cache.
There are two problems that I encountered in moving to slub: 1) I want to keep each mount point separate, but slub just hooks up with an existing cache of the same size. I managed to trick slub into keeping yaffs objects in their own cache by assigning a fake ctor. That stops the combination (well at present anyway - could easy change in the future like if ctor gets dropped). Like a VW Bug: ugly but it gets you there....
2) If I dump a cache with existing in-use objects then slub gets upset and dumps warnings. I don't like the idea of just ignoring warnings. I also don't want to manually tear down trees etc when the existing "just dump it" approach is a lot faster. Pity there is no "trust me I know what I'm doing" flag.
Questions: A) Is there a better way to use slub to do this or is it better to just continue with my manual allocator?
B) Is it worth adding flags to kmem_cache_create() to say: a) Don't combine this slub with others. b) "Trust me I know what I'm doing": Allow the cache to be dumped with objects still allocated.
If (B) makes sense I'll put together a patch.
-- Charles
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