Date: Thu, 21 Jun 2012 08:16:22 -0400 From: John Baldwin <jhb@freebsd.org> To: Venkat Duvvuru <venkatduvvuru.ml@gmail.com> Cc: freebsd-net@freebsd.org Subject: Re: MSI-X limitation in freebsd 8.2 Message-ID: <201206210816.22774.jhb@freebsd.org> In-Reply-To: <CAGdae7anhqdzacVt-BMv3e7GvKFO4QbYEVxd9k-agGjLfPi_iQ@mail.gmail.com> References: <CAGdae7YW0jt4gTmHufHFTrcdtFGhngu_Wi%2BMDg1nY_T0J1C_SQ@mail.gmail.com> <201206201054.40824.jhb@freebsd.org> <CAGdae7anhqdzacVt-BMv3e7GvKFO4QbYEVxd9k-agGjLfPi_iQ@mail.gmail.com>
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On Thursday, June 21, 2012 5:47:48 am Venkat Duvvuru wrote:
> John - Thanks for the reply.
>
> All the CPUs are ~100% idle. I don't see any interrupt storm on any of the
> irqs (vmstat -i).
>
> One observation I made is that I see messages like these in dmesg
>
> ===> mem 0xfaf60000-0xfaf7ffff,0xfaf40000-0xfaf5ffff,0xfaf1c000-0xfaf1ffff
> irq 40 at device 0.1 on pci6
>
> Looking at the irq value I think it is the INTx irq range which shouldn't
> have probably got allocated as the device is msix capable and there are
> vectors allocated for these devices in the range (256-380).
>
> Could this be a problem?
No, that line is output before the driver's attach routine is run, so it will
always show INTx IRQ value even if it isn't used.
> The scenario where I am hitting this problem is a setup with 4 NICs, each
> NIC with two ports and each port using up 4 msix vectors. The system is
> fine till some ports are up but once I ifup the 5th port, the system
> becomes sluggish.
>
> I'm not sure whether all the 30 vectors are from a single cpu..I don't know
> how to get that information.
Unfortunately there isn't an easy way. I have this gdb script which can
display it from kgdb on x86:
define irqs
set $e = event_list->tqh_first
while ($e != 0)
if ($e->ie_source != 0 && $e->ie_handlers.tqh_first != 0)
set $src = (struct intsrc *)$e->ie_source
if ($src->is_pic->pic_enable_source == &ioapic_enable_source)
set $_cpu = ((struct ioapic_intsrc *)$src)->io_cpu
else
if ($src->is_pic->pic_enable_source == &msi_enable_source)
set $_cpu = ((struct msi_intsrc *)$src)->msi_cpu
else
set $_cpu = 0
end
end
printf "CPU %d: %s\n", $_cpu, $e->ie_fullname
end
set $e = $e->ie_list.tqe_next
end
end
document irqs
Dump list of IRQs with associated CPU.
end
However, unless the driver is using BUS_BIND_IRQ() or you are using cpuset -x,
the interrupts should be round-robin assigned among CPUs.
What exactly do you mean by sluggish? Trying to interact with the box over
SSH is sluggish? Is there a change in RTT if you are pinging the box, is
there a change in performance of TCP or UDP streams to/from the box?
--
John Baldwin
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