Re: Interesting data on network interrupt - part II

From: John Baldwin <jhb_at_freebsd.org>
Date: Wed, 5 Apr 2006 16:38:57 -0400
On Tuesday 04 April 2006 20:33, Paolo Pisati wrote:
> Hi, 
> 
> i updated my work on interrupt profiling with sone new
> experiments.
> 
> In total we have now:
> 
> -FreeBSD 4 PIC (no asm part)
> -FreeBSD 7 APIC 
> -FreeBSD 7 PIC
> -FreeBSD 7 PREE APIC
> -FreeBSD 7 APIC JHB
> 
> Some quick comments:
> 
> -PIC is much slower in masking interrupt (7k in PIC vs 3k in APIC)
> -PREE let new thread save less than 500 ticks of 'queue' while 
>  preempted threads are often resumed after a lot
> -JHB patch shaved 2.5k ticks in interrupt masking op
> 
> For graphs, data and more comments:
> 
> http://mercurio.sm.dsi.unimi.it/~pisati/interrupt/

I'll commit the patch then. :)  One thing you might try to do to better
measure the effects of preemption is to generate kernel work so that
the bge interrupts occur while the current thread is in the kernel
rather than in userland.  In that case preemption should provide much
lower latency for interrupt handlers, as w/o preemption, an interrupt
in kernel mode won't run the ithread until either curthread blocks or
returns to userland.

-- 
John Baldwin <jhb_at_FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org
Received on Wed Apr 05 2006 - 18:39:12 UTC

This archive was generated by hypermail 2.4.0 : Wed May 19 2021 - 11:38:54 UTC