Re: Wierd context-switching issue on Xeon - Mailing list pgsql-performance

Tom Lane wrote:
>
> Hmmm ... I've been able to reproduce the CS storm on a dual Athlon,
> which seems to pretty much let the Xeon per se off the hook.  Anybody
> got a multiple Opteron to try?  Totally non-Intel CPUs?
>
> It would be interesting to see results with non-Linux kernels, too.
>
>             regards, tom lane

I also tested on an dual Athlon MP Tyan Thunder motherboard (2xMP2800+,
2.5GB memory), and got the same high numbers.
I then ran with kernel 2.6.5, it lowered them a little, but it's still
some ping pong effect here. I wonder if this is some effect of the
scheduler, maybe the shed frequency alone (100HZ vs 1000HZ).

It would be interesting to see what a locking implementation ala FUTEX
style would give on an 2.6 kernel, as i understood it that would work
cross process with some work.

The first file attached is kernel 2.4 running one process then starting
up the other one.
Same with second file, but with kernel 2.6...

Regards
Magnus
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
 1  0      0 1828408  27852 528852    0    0     0     0  317   557 50  0 50  0
 1  0      0 1828408  27852 528852    0    0     0     0  293   491 50  0 49  0
 1  0      0 1828400  27860 528852    0    0     0    16  399   709 50  0 50  0
 1  0      0 1828400  27860 528852    0    0     0     0  350   593 50  0 49  0
 2  0      0 1828400  27860 528852    0    0     0     0  349   608 50  0 50  0
 1  0      0 1828400  27860 528852    0    0     0     0  109   412 50  0 50  0
 1  0      0 1828400  27860 528852    0    0     0     0  101    92 50  0 50  0
 1  0      0 1828392  27868 528852    0    0     0    16  104    96 50  0 50  0
 1  0      0 1828392  27868 528852    0    0     0     0  101   103 50  0 50  0
 2  0      0 1827408  27892 528852    0    0     8    48  113 61197 45  9 46  0
 2  0      0 1827408  27892 528852    0    0     0     0  101 167237 41 27 32  0
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
 4  0      0 1827408  27892 528852    0    0     0     0  101 166145 39 25 36  0
 2  0      0 1827400  27900 528852    0    0     0    48  105 149406 42 19 40  0
 3  0      0 1827400  27900 528852    0    0     0     0  101 157559 43 26 32  0
 2  0      0 1827400  27900 528852    0    0     0     0  101 163813 46 24 30  0
 2  0      0 1827400  27900 528852    0    0     0     0  101 156872 44 26 30  0
 2  0      0 1827400  27900 528852    0    0     0     0  103 160722 45 28 28  0
 2  0      0 1827392  27908 528852    0    0     0    16  104 158644 41 23 37  0
 3  0      0 1827392  27908 528852    0    0     0     0  101 157534 42 25 33  0
 2  0      0 1827392  27908 528852    0    0     0     0  101 160007 37 28 35  0
 3  0      0 1827392  27908 528852    0    0     0     0  101 161852 45 24 31  0
 3  0      0 1827392  27908 528852    0    0     0     0  101 161616 42 25 33  0
 2  0      0 1827392  27916 528852    0    0     0    68  114 152144 44 25 31  0
 2  0      0 1827384  27916 528852    0    0     0     0  101 156485 35 28 37  0
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
 1  0      0 2436044   8844  90028    0    0     0    16 1010   235 50  0 50  0
 1  0      0 2436108   8844  90028    0    0     0     0 1024   404 50  0 50  0
 1  0      0 2436108   8844  90028    0    0     0     0 1008   199 50  0 50  0
 1  0      0 2436108   8844  90028    0    0     0     0 1017   272 50  0 50  0
 1  0      0 2436108   8844  90028    0    0     0     0 1013   253 50  0 50  0
 1  1      0 2436108   8852  90020    0    0     0    16 1019   282 51  0 49  1
 2  0      0 2435068   8852  90020    0    0     0     0 1005 23929 45  4 50  0
 2  0      0 2435068   8852  90020    0    0     0    20 1008 95501 33 14 53  0
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
 3  0      0 2435068   8852  90020    0    0     0     0 1002 103940 35 15 50  0
 0  0      0 2435068   8852  90020    0    0     0     0 1003 104343 32 16 51  0
 2  0      0 2435068   8860  90080    0    0     0    52 1006 102477 34 16 51  1
 2  0      0 2435068   8860  90080    0    0     0     0 1002 92809 31 14 54  0
 2  0      0 2435068   8860  90080    0    0     0     0 1002 100498 37 14 49  0
 1  0      0 2435068   8860  90080    0    0     0     0 1002 108130 35 16 49  0
 0  0      0 2435068   8860  90080    0    0     0     0 1002 94045 33 14 54  0
 0  0      0 2435004   8868  90072    0    0     0    16 1005 104380 34 15 52  0
 2  0      0 2435004   8868  90072    0    0     0     0 1002 100696 36 14 50  0
 2  0      0 2435068   8868  90072    0    0     0     0 1002 98289 31 14 54  0
 0  0      0 2435068   8868  90072    0    0     0     0 1002 97287 31 14 55  0
 0  0      0 2435068   8868  90072    0    0     0     0 1002 92787 34 14 53  0
 0  0      0 2435068   8876  90064    0    0     0    16 1005 98568 32 16 52  1
 2  0      0 2435068   8876  90064    0    0     0     0 1003 107104 37 16 47  0