lkml.org 
[lkml]   [2004]   [Jan]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Limit hash table size

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.

Anton
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:59    [W:0.085 / U:0.084 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site