Re: [PATCH] PCI/MSI: Export all remapped MSIs to sysfs attributes

Re: [PATCH] PCI/MSI: Export all remapped MSIs to sysfs attributes

[Bjorn Helgaas]

[+cc Neil, Thomas, linux-kernel]

Hi Romain,

On Thu, Sep 24, 2015 at 01:31:16AM +0200, Romain Bezut wrote:
> irqbalance uses these attributes to populate its internal database, which is
> then used to bind the irq on the appropriate NUMA node.
> 
> On a device accepting multiple MSIs and with interrupt remapping enabled,
> only the first irq entry is exported to msi_irqs directory.
> This results in irqbalance having no clue of the NUMA affinity for the extra
> irqs and starting to bind them on random nodes.
> 
> This patch exports all MSI interrupts as sysfs attributes when relevant.
> 
> Signed-off-by: Romain Bezut <rbezut@gmail.com>

This seems like it makes sense to me.  Do you have any bug reports
related to this problem?  If so, I'll mention them in the changelog.

Added Neil, Thomas, and linux-kernel since this is of interest to folks
beyond the usual linux-pci audience.

> ---
>  drivers/pci/msi.c | 31 +++++++++++++++++--------------
>  1 file changed, 17 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index d449714..324a164 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -475,10 +475,11 @@ static int populate_msi_sysfs(struct pci_dev *pdev)
>  	int ret = -ENOMEM;
>  	int num_msi = 0;
>  	int count = 0;
> +	int i;
>  
>  	/* Determine how many msi entries we have */
>  	for_each_pci_msi_entry(entry, pdev)
> -		++num_msi;
> +		num_msi += entry->nvec_used;
>  	if (!num_msi)
>  		return 0;
>  
> @@ -487,19 +488,21 @@ static int populate_msi_sysfs(struct pci_dev *pdev)
>  	if (!msi_attrs)
>  		return -ENOMEM;
>  	for_each_pci_msi_entry(entry, pdev) {
> -		msi_dev_attr = kzalloc(sizeof(*msi_dev_attr), GFP_KERNEL);
> -		if (!msi_dev_attr)
> -			goto error_attrs;
> -		msi_attrs[count] = &msi_dev_attr->attr;
> -
> -		sysfs_attr_init(&msi_dev_attr->attr);
> -		msi_dev_attr->attr.name = kasprintf(GFP_KERNEL, "%d",
> -						    entry->irq);
> -		if (!msi_dev_attr->attr.name)
> -			goto error_attrs;
> -		msi_dev_attr->attr.mode = S_IRUGO;
> -		msi_dev_attr->show = msi_mode_show;
> -		++count;
> +		for (i = 0; i < entry->nvec_used; i++) {
> +			msi_dev_attr = kzalloc(sizeof(*msi_dev_attr), GFP_KERNEL);
> +			if (!msi_dev_attr)
> +				goto error_attrs;
> +			msi_attrs[count] = &msi_dev_attr->attr;
> +
> +			sysfs_attr_init(&msi_dev_attr->attr);
> +			msi_dev_attr->attr.name = kasprintf(GFP_KERNEL, "%d",
> +							    entry->irq + i);
> +			if (!msi_dev_attr->attr.name)
> +				goto error_attrs;
> +			msi_dev_attr->attr.mode = S_IRUGO;
> +			msi_dev_attr->show = msi_mode_show;
> +			++count;
> +		}
>  	}
>  
>  	msi_irq_group = kzalloc(sizeof(*msi_irq_group), GFP_KERNEL);
> -- 
> 2.4.9
> 
> --
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Re: [PATCH] PCI/MSI: Export all remapped MSIs to sysfs attributes

[Thomas Gleixner]

On Fri, 9 Oct 2015, Bjorn Helgaas wrote:
> On Thu, Sep 24, 2015 at 01:31:16AM +0200, Romain Bezut wrote:
> > irqbalance uses these attributes to populate its internal database, which is
> > then used to bind the irq on the appropriate NUMA node.
> > 
> > On a device accepting multiple MSIs and with interrupt remapping enabled,
> > only the first irq entry is exported to msi_irqs directory.
> > This results in irqbalance having no clue of the NUMA affinity for the extra
> > irqs and starting to bind them on random nodes.
> > 
> > This patch exports all MSI interrupts as sysfs attributes when relevant.
> > 
> > Signed-off-by: Romain Bezut <rbezut@gmail.com>
> 
> This seems like it makes sense to me.  Do you have any bug reports
> related to this problem?  If so, I'll mention them in the changelog.
> 
> Added Neil, Thomas, and linux-kernel since this is of interest to folks
> beyond the usual linux-pci audience.

Acked-by: Thomas Gleixner <tglx@linutronix.de>

Re: [PATCH] PCI/MSI: Export all remapped MSIs to sysfs attributes

[Myron Stowe]

On Thu, Oct 15, 2015 at 11:23 AM, Bjorn Helgaas <helgaas@kernel.org> wrote:
> On Thu, Sep 24, 2015 at 01:31:16AM +0200, Romain Bezut wrote:
>> irqbalance uses these attributes to populate its internal database, which is
>> then used to bind the irq on the appropriate NUMA node.
>>
>> On a device accepting multiple MSIs and with interrupt remapping enabled,
>> only the first irq entry is exported to msi_irqs directory.
>> This results in irqbalance having no clue of the NUMA affinity for the extra
>> irqs and starting to bind them on random nodes.
>>
>> This patch exports all MSI interrupts as sysfs attributes when relevant.
>>
>> Signed-off-by: Romain Bezut <rbezut@gmail.com>
>
> Applied with Thomas' ack to pci/msi for v4.4, thanks, Romain!

Internal testing with netperf - network performance between two
machines with 10Gb Intel NICs running 24 instances of the netperf tool
in parallel (to utilize all CPU cores) - shows a roughly 20%
performance degradation.  Bi-section showed the offending commit to be
this patch: commit a86760664f4 ("PCI/MSI: Export all remapped MSIs to
sysfs attributes").

  Prior: 9.62 +-0.00 gbits/sec
  After: 7.77 +-0.17 gbits/sec

>> ---
>>  drivers/pci/msi.c | 31 +++++++++++++++++--------------
>>  1 file changed, 17 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
>> index d449714..324a164 100644
>> --- a/drivers/pci/msi.c
>> +++ b/drivers/pci/msi.c
>> @@ -475,10 +475,11 @@ static int populate_msi_sysfs(struct pci_dev *pdev)
>>       int ret = -ENOMEM;
>>       int num_msi = 0;
>>       int count = 0;
>> +     int i;
>>
>>       /* Determine how many msi entries we have */
>>       for_each_pci_msi_entry(entry, pdev)
>> -             ++num_msi;
>> +             num_msi += entry->nvec_used;
>>       if (!num_msi)
>>               return 0;
>>
>> @@ -487,19 +488,21 @@ static int populate_msi_sysfs(struct pci_dev *pdev)
>>       if (!msi_attrs)
>>               return -ENOMEM;
>>       for_each_pci_msi_entry(entry, pdev) {
>> -             msi_dev_attr = kzalloc(sizeof(*msi_dev_attr), GFP_KERNEL);
>> -             if (!msi_dev_attr)
>> -                     goto error_attrs;
>> -             msi_attrs[count] = &msi_dev_attr->attr;
>> -
>> -             sysfs_attr_init(&msi_dev_attr->attr);
>> -             msi_dev_attr->attr.name = kasprintf(GFP_KERNEL, "%d",
>> -                                                 entry->irq);
>> -             if (!msi_dev_attr->attr.name)
>> -                     goto error_attrs;
>> -             msi_dev_attr->attr.mode = S_IRUGO;
>> -             msi_dev_attr->show = msi_mode_show;
>> -             ++count;
>> +             for (i = 0; i < entry->nvec_used; i++) {
>> +                     msi_dev_attr = kzalloc(sizeof(*msi_dev_attr), GFP_KERNEL);
>> +                     if (!msi_dev_attr)
>> +                             goto error_attrs;
>> +                     msi_attrs[count] = &msi_dev_attr->attr;
>> +
>> +                     sysfs_attr_init(&msi_dev_attr->attr);
>> +                     msi_dev_attr->attr.name = kasprintf(GFP_KERNEL, "%d",
>> +                                                         entry->irq + i);
>> +                     if (!msi_dev_attr->attr.name)
>> +                             goto error_attrs;
>> +                     msi_dev_attr->attr.mode = S_IRUGO;
>> +                     msi_dev_attr->show = msi_mode_show;
>> +                     ++count;
>> +             }
>>       }
>>
>>       msi_irq_group = kzalloc(sizeof(*msi_irq_group), GFP_KERNEL);
>> --
>> 2.4.9
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-pci" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> --
> To unsubscribe from this list: send the line "unsubscribe linux-pci" in
> the body of a message to majordomo@vger.kernel.org
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Re: [PATCH] PCI/MSI: Export all remapped MSIs to sysfs attributes

[Neil Horman]

On Mon, Jan 23, 2017 at 01:57:28PM -0700, Myron Stowe wrote:
> On Thu, Oct 15, 2015 at 11:23 AM, Bjorn Helgaas <helgaas@kernel.org> wrote:
> > On Thu, Sep 24, 2015 at 01:31:16AM +0200, Romain Bezut wrote:
> >> irqbalance uses these attributes to populate its internal database, which is
> >> then used to bind the irq on the appropriate NUMA node.
> >>
> >> On a device accepting multiple MSIs and with interrupt remapping enabled,
> >> only the first irq entry is exported to msi_irqs directory.
> >> This results in irqbalance having no clue of the NUMA affinity for the extra
> >> irqs and starting to bind them on random nodes.
> >>
> >> This patch exports all MSI interrupts as sysfs attributes when relevant.
> >>
> >> Signed-off-by: Romain Bezut <rbezut@gmail.com>
> >
> > Applied with Thomas' ack to pci/msi for v4.4, thanks, Romain!
> 
> Internal testing with netperf - network performance between two
> machines with 10Gb Intel NICs running 24 instances of the netperf tool
> in parallel (to utilize all CPU cores) - shows a roughly 20%
> performance degradation.  Bi-section showed the offending commit to be
> this patch: commit a86760664f4 ("PCI/MSI: Export all remapped MSIs to
> sysfs attributes").
> 
>   Prior: 9.62 +-0.00 gbits/sec
>   After: 7.77 +-0.17 gbits/sec
> 


Hmm, any idea whats leading to the performance degradation?  Seems odd that
exposing that info should lead to reduced performance.  is irqbalance placing
the interrupts on a node that is inappropriate (i.e. making the wrong decision
based on the info exposed)?

Neil
 
> >> ---
> >>  drivers/pci/msi.c | 31 +++++++++++++++++--------------
> >>  1 file changed, 17 insertions(+), 14 deletions(-)
> >>
> >> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> >> index d449714..324a164 100644
> >> --- a/drivers/pci/msi.c
> >> +++ b/drivers/pci/msi.c
> >> @@ -475,10 +475,11 @@ static int populate_msi_sysfs(struct pci_dev *pdev)
> >>       int ret = -ENOMEM;
> >>       int num_msi = 0;
> >>       int count = 0;
> >> +     int i;
> >>
> >>       /* Determine how many msi entries we have */
> >>       for_each_pci_msi_entry(entry, pdev)
> >> -             ++num_msi;
> >> +             num_msi += entry->nvec_used;
> >>       if (!num_msi)
> >>               return 0;
> >>
> >> @@ -487,19 +488,21 @@ static int populate_msi_sysfs(struct pci_dev *pdev)
> >>       if (!msi_attrs)
> >>               return -ENOMEM;
> >>       for_each_pci_msi_entry(entry, pdev) {
> >> -             msi_dev_attr = kzalloc(sizeof(*msi_dev_attr), GFP_KERNEL);
> >> -             if (!msi_dev_attr)
> >> -                     goto error_attrs;
> >> -             msi_attrs[count] = &msi_dev_attr->attr;
> >> -
> >> -             sysfs_attr_init(&msi_dev_attr->attr);
> >> -             msi_dev_attr->attr.name = kasprintf(GFP_KERNEL, "%d",
> >> -                                                 entry->irq);
> >> -             if (!msi_dev_attr->attr.name)
> >> -                     goto error_attrs;
> >> -             msi_dev_attr->attr.mode = S_IRUGO;
> >> -             msi_dev_attr->show = msi_mode_show;
> >> -             ++count;
> >> +             for (i = 0; i < entry->nvec_used; i++) {
> >> +                     msi_dev_attr = kzalloc(sizeof(*msi_dev_attr), GFP_KERNEL);
> >> +                     if (!msi_dev_attr)
> >> +                             goto error_attrs;
> >> +                     msi_attrs[count] = &msi_dev_attr->attr;
> >> +
> >> +                     sysfs_attr_init(&msi_dev_attr->attr);
> >> +                     msi_dev_attr->attr.name = kasprintf(GFP_KERNEL, "%d",
> >> +                                                         entry->irq + i);
> >> +                     if (!msi_dev_attr->attr.name)
> >> +                             goto error_attrs;
> >> +                     msi_dev_attr->attr.mode = S_IRUGO;
> >> +                     msi_dev_attr->show = msi_mode_show;
> >> +                     ++count;
> >> +             }
> >>       }
> >>
> >>       msi_irq_group = kzalloc(sizeof(*msi_irq_group), GFP_KERNEL);
> >> --
> >> 2.4.9
> >>
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe linux-pci" in
> >> the body of a message to majordomo@vger.kernel.org
> >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-pci" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
>