Messages in this thread | | | Date | Tue, 25 Nov 2003 17:11:08 -0600 | From | Jack Steiner <> | Subject | Re: hash table sizes |
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On Wed, Nov 26, 2003 at 08:16:11AM +1100, Anton Blanchard wrote: > > Hi, > > > Some architectures (IA64, for example) dont have severe limitations on > > usage of vmalloc space. Would it make sense to use vmalloc on these > > architectures. Even if the max size of the structures being allocated > > is limited to an acceptible size, it still concentrates the memory on > > a single node. > > The kernel region on many architectures is mapped with large pages, we > would lose that by going to vmalloc. > > Anton
That was a concern to me too. However, on IA64, all page structs are in the vmalloc region (it isnt allocated by vmalloc but is in the same region as vmalloc'ed pages. They are mapped with 16k pages instead of the 64MB pages used for memory allocated by kmalloc).
Before switching to 16K pages for the page structs, we made numerous performance measurements. As far as we could tell, there was no performce degradation caused by the smaller pages. It seems to me that if page structs are ok being mapped by 16k pages, the hash tables would be ok too.
-- Thanks
Jack Steiner (steiner@sgi.com) 651-683-5302 Principal Engineer SGI - Silicon Graphics, Inc.
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