Thanks Jesper and David for reviewing and replying.
Great commitment of Jesper for moving above three hlist_nulls_heads to
percpu structure. Sorry to miss the newest advances in nf-next.
And arbitrarily cache-line aligning structure members is not a good idea
for large cache lines.
Still I have an idea that could we pack the seldom changed members
(nf_ct_proto included) to a structure and we allocated it from a
cache aligned slub when the structure "net" is initialized.
Zhouyi
On Wed, Mar 12, 2014 at 5:36 PM, David Laight <david.lai...@aculab.com> wrote:
> From: Zhouyi Zhou
>> not frequently changing components should share same cachelines
>>
>> Signed-off-by: Zhouyi Zhou <yizhouz...@ict.ac.cn>
>> ---
>> include/net/netns/conntrack.h | 12 ++++++++----
>> 1 file changed, 8 insertions(+), 4 deletions(-)
>>
>> diff --git a/include/net/netns/conntrack.h b/include/net/netns/conntrack.h
>> index fbcc7fa..69d2d58 100644
>> --- a/include/net/netns/conntrack.h
>> +++ b/include/net/netns/conntrack.h
>> @@ -65,6 +65,12 @@ struct nf_ip_net {
>> struct netns_ct {
>> atomic_t count;
>> unsigned int expect_count;
>> + struct hlist_nulls_head unconfirmed;
>> + struct hlist_nulls_head dying;
>> + struct hlist_nulls_head tmpl;
>> +
>> + /* not frequently changing components should share same cachelines */
>> + struct nf_ip_net nf_ct_proto ____cacheline_aligned_in_smp;
>
> I'm not sure this has the effect you are trying to achieve.
> Adding an __attribute__((aligned(n))) to a structure member not only
> adds padding before the member, but also pads the member to a multiple
> of the specified size.
>
> With large cache lines you probably want neither.
> IIRC one of the ppc systems has something like 256 byte cache lines
> (and if it doesn't now, it might have soon).
> So arbitrarily cache-line aligning structure members may not be a good idea.
>
> In any case reducing the number of cache lines accessed, and the number
> dirtied is probably more important than putting 'readonly' data in its
> own cache lines.
>
> David
>
>
>
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