MSI-X limitation in freebsd 8.2

[Venkat Duvvuru]

I suspected the hardware hence installed Linux and cross verified that
Linux is working fine.

/Venkat

On Thu, Jun 21, 2012 at 6:20 PM, Venkat Duvvuru
<venkatduvvuru.ml at gmail.com>wrote:

> While I'm able to ping to the machine..every command on the current active
> session is sluggish infact doesn't complete, unable to open another ssh
> session..an already opened ssh session doesn't react which is running
> "systat -vmstat"...
>
> The only thing I could do is to successfully complete "top -P" command
> once..even top hung for the second time.
>
> /Venkat
>
>
> On Thu, Jun 21, 2012 at 5:46 PM, John Baldwin <jhb at freebsd.org> wrote:
>
>> 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
>>
>
>