> On Thursday 30 June 2005 10:35 am, Andriy Tkachuk wrote:
> > I just checked the object code - you right, it almost the same:
> >
> > - bucket->ub_bucket[bucket->ub_cnt] = item;
> > - 22b9: 0f bf 43 08 movswl 0x8(%ebx),%eax
> > - 22bd: 8b 4d 0c mov 0xc(%ebp),%ecx
> > - 22c0: 89 4c 83 0c mov %ecx,0xc(%ebx,%eax,4)
> > - bucket->ub_cnt++;
> > - 22c4: 8d 42 01 lea 0x1(%edx),%eax
> > - 22c7: 66 89 43 08 mov %ax,0x8(%ebx)
> > + bucket->ub_bucket[bucket->ub_cnt++] = item;
> > + 22b9: 0f bf c2 movswl %dx,%eax
> > + 22bc: 8b 4d 0c mov 0xc(%ebp),%ecx
> > + 22bf: 89 4c 83 0c mov %ecx,0xc(%ebx,%eax,4)
> > + 22c3: 8d 42 01 lea 0x1(%edx),%eax
> > + 22c6: 66 89 43 08 mov %ax,0x8(%ebx)
> >
> > but still there is some minor difference in first line.
> > I'm not familiar with assembler, can somebody explain
> > whether this difference is assential or not?
>
> It just uses the stored value of the variable in %dx instead of loading it
> from memory at 0x8(%ebx). When I compiled a simple test program here locally
> I got identical object code though.
Probaly this is the reason of throughput increasing.
I want to note, that all tests where made on my home workstation.
And each new test was made with new kernel just after rebooting
in ttyv withoud X-server.
I think the noise was not assential.
Ministats against second & third optimization showed this results:
(for different number of sockets created & destroyed in one iteration)
> /usr/src/tools/tools/ministat/ministat -c 99.5 sockloop_stat2_o1_sys_1000
> sockloop_stat2_o2_sys_1000
x sockloop_stat2_o1_sys_1000
+ sockloop_stat2_o2_sys_1000
+--------------------------------------------------------------------------+
|+ + + x x x|
||______________A_____________| |_______M__A__________| |
+--------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 3 2.373 2.403 2.381 2.3856667 0.015534907
+ 3 2.298 2.34 2.32 2.3193333 0.021007935
No difference proven at 99.5% confidence
> /usr/src/tools/tools/ministat/ministat -c 99.5 sockloop_stat2_o1_sys_100
> sockloop_stat2_o2_sys_100
x sockloop_stat2_o1_sys_100
+ sockloop_stat2_o2_sys_100
+--------------------------------------------------------------------------+
|+ + + x x x |
| |___________________A__M_______________| |_______AM_____||
+--------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 3 2.158 2.182 2.174 2.1713333 0.012220202
+ 3 2.062 2.126 2.102 2.0966667 0.032331615
No difference proven at 99.5% confidence
> /usr/src/tools/tools/ministat/ministat -c 99.5 sockloop_stat2_o1_sys_10
> sockloop_stat2_o2_sys_10
x sockloop_stat2_o1_sys_10
+ sockloop_stat2_o2_sys_10
+--------------------------------------------------------------------------+
| + |
| + + x xx |
||_M_A____| |________A___M___||
+--------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 3 1.754 1.777 1.776 1.769 0.013
+ 3 1.672 1.684 1.673 1.6763333 0.0066583281
Difference at 99.5% confidence
-0.0926667 +/- 0.060488
-5.23836% +/- 3.41934%
(Student's t, pooled s = 0.010328)
> /usr/src/tools/tools/ministat/ministat -c 99.5 sockloop_stat2_o1_sys_1
> sockloop_stat2_o2_sys_1
x sockloop_stat2_o1_sys_1
+ sockloop_stat2_o2_sys_1
+--------------------------------------------------------------------------+
|+ + + x x x|
||________AM_______| |____M_A_______| |
+--------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 3 1.938 1.993 1.953 1.9613333 0.028431204
+ 3 1.722 1.785 1.759 1.7553333 0.031659648
Difference at 99.5% confidence
-0.206 +/- 0.176222
-10.5031% +/- 8.98479%
(Student's t, pooled s = 0.0300888)
and for default confidence (95%) this results:
> /usr/src/tools/tools/ministat/ministat sockloop_stat2_o1_sys_1000
> sockloop_stat2_o2_sys_1000
x sockloop_stat2_o1_sys_1000
+ sockloop_stat2_o2_sys_1000
+--------------------------------------------------------------------------+
|+ + + x x x|
||______________A_____________| |_______M__A__________| |
+--------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 3 2.373 2.403 2.381 2.3856667 0.015534907
+ 3 2.298 2.34 2.32 2.3193333 0.021007935
Difference at 95.0% confidence
-0.0663333 +/- 0.0418758
-2.78049% +/- 1.75531%
(Student's t, pooled s = 0.0184752)
> /usr/src/tools/tools/ministat/ministat sockloop_stat2_o1_sys_100
> sockloop_stat2_o2_sys_100
x sockloop_stat2_o1_sys_100
+ sockloop_stat2_o2_sys_100
+--------------------------------------------------------------------------+
|+ + + x x x |
| |___________________A__M_______________| |_______AM_____||
+--------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 3 2.158 2.182 2.174 2.1713333 0.012220202
+ 3 2.062 2.126 2.102 2.0966667 0.032331615
Difference at 95.0% confidence
-0.0746667 +/- 0.0553965
-3.43875% +/- 2.55127%
(Student's t, pooled s = 0.0244404)
Resume: the difference is present and it is more for smaller
deviations in balanced allocs & frees. It is up to 10% if deviation is minimal.
--
Andriy Tkachuk.
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