Date: Thu, 13 Nov 2008 19:55:01 +0800 From: "Archimedes Gaviola" <archimedes.gaviola@gmail.com> To: "John Baldwin" <jhb@freebsd.org> Cc: freebsd-smp@freebsd.org Subject: Re: CPU affinity with ULE scheduler Message-ID: <42e3d810811130355x3857bceap447e134b18eee04b@mail.gmail.com> In-Reply-To: <200811111216.37462.jhb@freebsd.org> References: <42e3d810811100033w172e90dbl209ecbab640cc24f@mail.gmail.com> <200811101733.04547.jhb@freebsd.org> <42e3d810811102032w7850a1c0t386d80ce747f37d3@mail.gmail.com> <200811111216.37462.jhb@freebsd.org>
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On Wed, Nov 12, 2008 at 1:16 AM, John Baldwin <jhb@freebsd.org> wrote:
> On Monday 10 November 2008 11:32:55 pm Archimedes Gaviola wrote:
>> On Tue, Nov 11, 2008 at 6:33 AM, John Baldwin <jhb@freebsd.org> wrote:
>> > On Monday 10 November 2008 03:33:23 am Archimedes Gaviola wrote:
>> >> To Whom It May Concerned:
>> >>
>> >> Can someone explain or share about ULE scheduler (latest version 2 if
>> >> I'm not mistaken) dealing with CPU affinity? Is there any existing
>> >> benchmarks on this with FreeBSD? Because I am currently using 4BSD
>> >> scheduler and as what I have observed especially on processing high
>> >> network load traffic on multiple CPU cores, only one CPU were being
>> >> stressed with network interrupt while the rests are mostly in idle
>> >> state. This is an AMD-64 (4x) dual-core IBM system with GigE Broadcom
>> >> network interface cards (bce0 and bce1). Below is the snapshot of the
>> >> case.
>> >
>> > Interrupts are routed to a single CPU. Since bce0 and bce1 are both on
> the
>> > same interrupt (irq 23), the CPU that interrupt is routed to is going to
> end
>> > up handling all the interrupts for bce0 and bce1. This not something ULE
> or
>> > 4BSD have any control over.
>> >
>> > --
>> > John Baldwin
>> >
>>
>> Hi John,
>>
>> I'm sorry for the wrong snapshot. Here's the right one with my concern.
>>
>> PID USERNAME THR PRI NICE SIZE RES STATE C TIME WCPU COMMAND
>> 17 root 1 171 52 0K 16K CPU0 0 54:28 95.17% idle: cpu0
>> 15 root 1 171 52 0K 16K CPU2 2 55:55 93.65% idle: cpu2
>> 14 root 1 171 52 0K 16K CPU3 3 58:53 93.55% idle: cpu3
>> 13 root 1 171 52 0K 16K RUN 4 59:14 82.47% idle: cpu4
>> 12 root 1 171 52 0K 16K RUN 5 55:42 82.23% idle: cpu5
>> 16 root 1 171 52 0K 16K CPU1 1 58:13 77.78% idle: cpu1
>> 11 root 1 171 52 0K 16K CPU6 6 54:08 76.17% idle: cpu6
>> 36 root 1 -68 -187 0K 16K WAIT 7 8:50 65.53%
>> irq23: bce0 bce1
>> 10 root 1 171 52 0K 16K CPU7 7 48:19 29.79% idle: cpu7
>> 43 root 1 171 52 0K 16K pgzero 2 0:35 1.51% pagezero
>> 1372 root 10 20 0 16716K 5764K kserel 6 58:42 0.00% kmd
>> 4488 root 1 96 0 30676K 4236K select 2 1:51 0.00% sshd
>> 18 root 1 -32 -151 0K 16K WAIT 0 1:14 0.00% swi4:
> clock s
>> 20 root 1 -44 -163 0K 16K WAIT 0 0:30 0.00% swi1: net
>> 218 root 1 96 0 3852K 1376K select 0 0:23 0.00% syslogd
>> 2171 root 1 96 0 30676K 4224K select 6 0:19 0.00% sshd
>>
>> Actually I was doing a network performance testing on this system with
>> FreeBSD-6.2 RELEASE using its default scheduler 4BSD and then I used a
>> tool to generate big amount of traffic around 600Mbps-700Mbps
>> traversing the FreeBSD system in bi-direction, meaning both network
>> interfaces are receiving traffic. What happened was, the CPU (cpu7)
>> that handles the (irq 23) on both interfaces consumed big amount of
>> CPU utilization around 65.53% in which it affects other running
>> applications and services like sshd and httpd. It's no longer
>> accessible when traffic is bombarded. With the current situation of my
>> FreeBSD system with only one CPU being stressed, I was thinking of
>> moving to FreeBSD-7.0 RELEASE with the ULE scheduler because I thought
>> my concern has something to do with the distributions of load on
>> multiple CPU cores handled by the scheduler especially at the network
>> level, processing network load. So, if it is more of interrupt
>> handling and not on the scheduler, is there a way we can optimize it?
>> Because if it still routed only to one CPU then for me it's still
>> inefficient. Who handles interrupt scheduling for bounding CPU in
>> order to prevent shared IRQ? Is there any improvements with
>> FreeBSD-7.0 with regards to interrupt handling?
>
> It depends. In all likelihood, the interrupts from bce0 and bce1 are both
> hardwired to the same interrupt pin and so they will always share the same
> ithread when using the legacy INTx interrupts. However, bce(4) parts do
> support MSI, and if you try a newer OS snap (6.3 or later) these devices
> should use MSI in which case each NIC would be assigned to a separate CPU. I
> would suggest trying 7.0 or a 7.1 release candidate and see if it does
> better.
>
> --
> John Baldwin
>
Hi John,
I try 7.0 release and each network interface were already allocated
separately on different CPU. Here, MSI is already working.
PID USERNAME THR PRI NICE SIZE RES STATE C TIME WCPU COMMAND
12 root 1 171 ki31 0K 16K CPU6 6 123:55 100.00% idle: cpu6
15 root 1 171 ki31 0K 16K CPU3 3 123:54 100.00% idle: cpu3
14 root 1 171 ki31 0K 16K CPU4 4 123:26 100.00% idle: cpu4
16 root 1 171 ki31 0K 16K CPU2 2 123:15 100.00% idle: cpu2
17 root 1 171 ki31 0K 16K CPU1 1 123:15 100.00% idle: cpu1
37 root 1 -68 - 0K 16K CPU7 7 9:09 100.00% irq256: bce0
13 root 1 171 ki31 0K 16K CPU5 5 123:49 99.07% idle: cpu5
40 root 1 -68 - 0K 16K WAIT 0 4:40 51.17% irq257: bce1
18 root 1 171 ki31 0K 16K RUN 0 117:48 49.37% idle: cpu0
11 root 1 171 ki31 0K 16K RUN 7 115:25 0.00% idle: cpu7
19 root 1 -32 - 0K 16K WAIT 0 0:39 0.00% swi4: clock s
14367 root 1 44 0 5176K 3104K select 2 0:01 0.00% dhcpd
22 root 1 -16 - 0K 16K - 3 0:01 0.00% yarrow
25 root 1 -24 - 0K 16K WAIT 0 0:00 0.00% swi6: Giant t
11658 root 1 44 0 32936K 4540K select 1 0:00 0.00% sshd
14224 root 1 44 0 32936K 4540K select 5 0:00 0.00% sshd
41 root 1 -60 - 0K 16K WAIT 0 0:00 0.00% irq1: atkbd0
4 root 1 -8 - 0K 16K - 2 0:00 0.00% g_down
The bce0 interface interrupt (irq256) gets stressed out which already
have 100% of CPU7 while CPU0 is around 51.17%. Any more
recommendations? Is there anything we can do about optimization with
MSI?
Thanks,
Archimedes
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