Re: [thisops uV2 02/10] vmstat: Optimize zone counter modificationsthrough the use of this cpu operations

[Christoph Lameter]

Some numbers for the cmpxchg implementation (cycles)

Function		Orig	Cmpxchg Fallback
--------------------------------------------------
inc_zone_page_state	170	32	196
__inc_zone_page_s	23	31	26
inc/dec pairs		347	69	379

So the fallback is always worse. cmpxchg is only better for the versions
of zone counters where we need to disable and enable interrupts.

This would suggest to only use the cmpxchg for arches that have cmpxchg
local and only in the case of the full versions.

There are 12 cases of inc_zone_page_state and 13 of dec_zone_page_state
as well as 7 cases of mod_zone_page_state.


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