Re: [PATCH] MM : alloc_large_system_hash() can free some memory fornon power-of-two bucketsize
From: Eric Dumazet
Date: Sat May 19 2007 - 14:43:47 EST
William Lee Irwin III a écrit :
On Fri, May 18, 2007 at 11:54:54AM +0200, Eric Dumazet wrote:
alloc_large_system_hash() is called at boot time to allocate space
for several large hash tables.
Lately, TCP hash table was changed and its bucketsize is not a
power-of-two anymore.
On most setups, alloc_large_system_hash() allocates one big page
(order > 0) with __get_free_pages(GFP_ATOMIC, order). This single
high_order page has a power-of-two size, bigger than the needed size.
We can free all pages that wont be used by the hash table.
On a 1GB i386 machine, this patch saves 128 KB of LOWMEM memory.
TCP established hash table entries: 32768 (order: 6, 393216 bytes)
The proper way to do this is to convert the large system hashtable
users to use some data structure / algorithm other than hashing by
separate chaining.
No thanks. This was already discussed to death on netdev. To date, hash tables
are a good compromise.
I dont mind losing part of memory, I prefer to keep good performance when
handling 1.000.000 or more tcp sessions.
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