Messages in this thread | | | Date | Sat, 10 Jan 2004 01:25:45 +1100 | From | Anton Blanchard <> | Subject | Re: Limit hash table size |
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Hi,
> Last time I checked, the tcp ehash table is taking a whooping (insane!) > 2GB on one of our large machine. dentry and inode hash tables also take > considerable amount of memory. > > This patch just enforces all the hash tables to have a max order of 10, > which limits them down to 16MB each on ia64. People can clean up other > part of table size calculation. But minimally, this patch doesn't > change any hash sizes already in use on x86.
By limiting it by order you are crippling ppc64 compared to ia64 :) Perhaps we should limit it by size instead.
Have you done any analysis of hash depths of large memory machines? We had some extremely deep pagecache hashchains in 2.4 on a 64GB machine. While the radix tree should fix that, whos to say we cant get into a similar situation with the dcache?
Check out how deep some of the inode hash chains are here:
http://www.ussg.iu.edu/hypermail/linux/kernel/0312.0/0105.html
That was on a 64GB box from memory. Switch to the current high end, say 512GB and those chains could become a real dogs breakfast, especially if we limit the hashtable to 4MB.
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