On Wed, Oct 31, 2012 at 8:31 PM, Andre Oppermann <an...@freebsd.org> wrote: > On 31.10.2012 20:40, Ian Lepore wrote: >> >> On Thu, 2012-11-01 at 06:30 +1100, Peter Jeremy wrote: >>> >>> On 2012-Oct-31 18:57:37 +0000, Attilio Rao <atti...@freebsd.org> wrote: >>>> >>>> On 10/31/12, Adrian Chadd <adr...@freebsd.org> wrote: >>>>> >>>>> Right, but you didn't make it configurable for us embedded peeps who >>>>> still care about memory usage. >>>> >>>> >>>> How is this possible without breaking the module/kernel ABI? >>> >>> >>> Memory usage may override ABI compatibility in an embedded environment. >>> >>>> All that assuming you can actually prove a real performance loss even >>>> in the new cases. >>> >>> >>> The issue with padding on embedded systems is memory utilisation rather >>> than performance. >>> >> >> There are potential performance hits too, in that embedded systems tend >> to have tiny caches (16K L1 with no L2, that sort of thing), so >> purposely padding things so that large parts of a cache line aren't used >> for anything wastes a scarce resource. > > > You can define CACHE_LINE_SIZE to 0 on those platforms. > Or to make it even more granular there could be a CACHE_LINE_SIZE_LOCKS > that is used for lock padding.
I think that this is a bright idea, albeit under the condition that just like CACHE_LINE_SIZE it won't change during STABLE branches timeframe and that it must not be dependent by SMP option. What do you think about this patch?: http://www.freebsd.org/~attilio/cache_line_size_locks.patch Thanks, Attilio -- Peace can only be achieved by understanding - A. Einstein _______________________________________________ svn-src-all@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
