pipe and af/unix latency differences between aa and jam on smp
Quoted 11 lines
*Local* Communication latencies in microseconds - smaller is better
kernel Pipe AF/Unix
----------------------------- ------- -------2.4.19-pre7-jam6 29.513 42.369 2.4.19-pre8-jam2 7.697 15.274 2.4.19-pre8-jam2-nowuos 7.739 14.929(last line says that wake-up-sync is not responsible...)
Main changes between first two were irqbalance and
ide6->ide10.
The system is scsi only. pre7-jam6 and pre8-jam2 .config's were identical.
Quoted 1 line
Could you try latest -rc1-aa2 ? It includes also irqbalance,
Based on Andrea'a diff logs, irqbalance appeared in 2.4.19pre10aa3. There are small differences between the pre10-jam2 and aa irqbalance patches. One new datapoint with pre10-jam3:
*Local* Communication latencies in microseconds - smaller is better
-------------------------------------------------------------------
kernel Pipe AF/Unix
----------------------------- ------- -------
2.4.19-pre10-jam2 7.877 16.699 2.4.19-pre10-jam3 33.133 66.825 2.4.19-pre10-aa2 34.208 62.732 2.4.19-pre10-aa4 33.941 70.216 2.4.19-rc1-aa1-1g-nio 34.989 52.704
A config difference between pre10-jam2 and pre10-jam3 is:CONFIG_X86_SFENCE=y # pre10-jam2
pre10-jam2 was compiled with -Os and pre10-jam3 with -O2.
Quoted 1 line
Out of interest, is that a P4/Xeon?
Quad P3/Xeon 700 mhz with 1MB cache.
Signature · 2 lines
Randy Hron http://home.earthlink.net/~rwhron/kernel/bigbox.html
Quoted 25 lines · On Tue, Jul 09, 2002 at 10:05:58AM -0400, [email protected] wrote:
Quoted 11 lines
*Local* Communication latencies in microseconds - smaller is better
kernel Pipe AF/Unix
----------------------------- ------- -------2.4.19-pre7-jam6 29.513 42.369 2.4.19-pre8-jam2 7.697 15.274 2.4.19-pre8-jam2-nowuos 7.739 14.929(last line says that wake-up-sync is not responsible...)
Main changes between first two were irqbalance and
ide6->ide10.The system is scsi only. pre7-jam6 and pre8-jam2 .config's were identical.
Quoted 1 line
Could you try latest -rc1-aa2 ? It includes also irqbalance,
Based on Andrea'a diff logs, irqbalance appeared in 2.4.19pre10aa3. There are small differences between the pre10-jam2 and aa irqbalance patches. One new datapoint with pre10-jam3:
*Local* Communication latencies in microseconds - smaller is better
-------------------------------------------------------------------
kernel Pipe AF/Unix
----------------------------- ------- -------
Quoted 5 lines
2.4.19-pre10-jam2 7.877 16.699 2.4.19-pre10-jam3 33.133 66.825 2.4.19-pre10-aa2 34.208 62.732 2.4.19-pre10-aa4 33.941 70.216 2.4.19-rc1-aa1-1g-nio 34.989 52.704
now if this was AF_INET via ethernet I could imagine the irqbalance making difference (or even irqrate even if irqrate should make no difference until your hardware hits the limit of irqs it can handle).
but both pipe and afunix should not generate any irq load (other than the IPI with the reschedule_task wakeups at least, but they're only dependent on the scheduler, ipi delivery isn't influenced by the irqrate/irqbalance patches). it's all trasmission in software internal to the kernel, with no hardware events so no irq, so I would be very surprised if the irqbalance or irqrate could make any difference. I would look elsewere first at least. No idea why you're looking at those irq related patches for this workload.
At first glance I would say either it's a compiler issue that generates some very inefficent code one way or the other (seems very unlikely but cache effects can be quite huge in tight loops where a very small part of the kernel is exercised), or it has something to do with schduler or similar core non-irq related areas.
Quoted 12 lines
A config difference between pre10-jam2 and pre10-jam3 is:
CONFIG_X86_SFENCE=y# pre10-jam2
pre10-jam2 was compiled with -Os and pre10-jam3 with -O2.Quoted 1 line
Out of interest, is that a P4/Xeon?
Quad P3/Xeon 700 mhz with 1MB cache.
Signature · 2 lines
Randy Hron http://home.earthlink.net/~rwhron/kernel/bigbox.html
Andrea