On 25.04.2013 07:40, Olivier Cochard-Labbé wrote:
On Wed, Apr 24, 2013 at 1:46 PM, Sami Halabi <sodyn...@gmail.com> wrote:
3. there some point of improved performance (without fw) that went down
again somewhere before Clang got prod.
Found it !
It's commit 242402: "Rework the known mutexes..."
Again one has to be really careful drawing any firm conclusions from this
as it was measured on a Pentium4 and UP kernel (GENERIC would add WITNESS
and INVARIANT overhead as well).
The Pentium4 is about the worst micro-architecture when it comes to locks
and easily regresses. At the same time modern Intel Core i[3-7] and AMD64
may actually improve with these changes. Unless more recent micro-archs
have been shown to exhibit the same regression we can't claim this change
was bad (other than for Pentium4).
--
Andre
ministat -s 242401.forwarding 242402.forwarding
x 242401.forwarding
+ 242402.forwarding
+---------------------------------------------------------------------------------------+
| +
|
|+ + + +
x xx x x|
|
|____A____| |
| |_____A_M___|
|
+---------------------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 5 417527 420242 418902 419074 1049.7974
+ 5 402211 404828 404096 403689 1237.6696
Difference at 95.0% confidence
-15385 +/- 1673.69
-3.67119% +/- 0.399377%
(Student's t, pooled s = 1147.58)
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