Eric Dumazet a écrit :
> Andi Kleen a écrit :
> 
>>> Using memnode_shift=33 would access only 2 bytes from this 
>>> memnodemap[], touching fewer cache lines (well , one cache line). 
>>> kfree() and friends would be slightly faster, at least cache friendly.
>>
>>
>>
>> Agreed. Please send a patch.
> 

My previous patch was not correct. Couly you please review this second version.

[PATCH] NUMA,x86_64 :
     Compute the highest possible value for memnode_shift,
     in order to reduce footprint of memnodemap[] to the minimum, thus
     making all users (phys_to_nid(), kfree()), more cache friendly.

Before the patch :

Node 0 MemBase 0000000000000000 Limit 00000001ffffffff
Node 1 MemBase 0000000200000000 Limit 00000003ffffffff
Using 23 for the hash shift. Max adder is 3ffffffff

After the patch :

Node 0 MemBase 0000000000000000 Limit 00000001ffffffff
Node 1 MemBase 0000000200000000 Limit 00000003ffffffff
Using 33 for the hash shift.

In this case, only 2 bytes of memnodemap[] are used, instead of 2048

Thank you

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>