svn commit: r281103 - head/sys/amd64/amd64

[Kurt Lidl]

On 4/6/15 1:42 AM, Bruce Evans wrote:
> On Mon, 6 Apr 2015, Eitan Adler wrote:
>
>> + a few people interested in the diff
>>
>> On 5 April 2015 at 02:55, Bruce Evans <brde at optusnet.com.au> wrote:
>>> On Sun, 5 Apr 2015, Eitan Adler wrote:
>>
>> I did not confirm the performance impact, but the submitter and others
>> indicated they saw a difference.
>>
>> Do you have specific data that shows that there was an improvement?
>
> Only micro-benchmark output that indicates little difference.  This
> is probably very MD (depending on write combining hardware), so you
> might only see a difference on some systems.
>
> I also have micro-benchmark output for network packets/second that
> shows 10% differences for the change of adding 1 byte of padding
> in code that is never executed.  This seems to be due to different
> cache misses.  To eliminate differences from this (except ones
> caused by actually running different code), create a reference
> version by padding the functions or data to be changed so that
> the change doesn't affect the address of anything except the
> internals of the changed parts.
>
> I might try a makeworld run to see if changing the non-temporal
> accesses in pagecopy and pagezero to cached.


I ran a few (total of 12) buildworld runs after this discussion.
I finally got around to posting the results to the original bug.

The data is here:

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=199151#c3

-Kurt