Re: [PATCH] RCU: remove alignment padding from rcu_data on 64 bitbuilds

[Richard Kennedy]

On Fri, 2011-05-06 at 08:20 +0200, Eric Dumazet wrote:
...
> We could shrink this structure more, converting some 64bit fields to
> 32bit ones.
> 
> Rationale is the algo is working well on 32bit arches, no need to use
> 64bit fields.
> 
> candidates : completed, gpnum, passed_quiesc_completed, qlen,
> qlen_last_fqs_check, blimit.
> 
> Counters might be converted too.

I don't know the code well enough to make that decision ;)
Is it possible to shrink it enough to free up another cache line ?
(16 longs to ints).

CONFIG_NO_HZ adds 24 bytes so even for users with !CONFIG_NO_HZ the
variables you suggest are not enough to free a cache line.  

regards
Richard


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