On Mon, Jun 02, 2014 at 09:52:06AM -0500, scame...@beardog.cce.hp.com wrote:
> On Mon, Jun 02, 2014 at 02:27:51AM -0700, Christoph Hellwig wrote:
> > On Thu, May 29, 2014 at 10:53:02AM -0500, Stephen M. Cameron wrote:
> > > From: Stephen M. Cameron <scame...@beardog.cce.hp.com>
> > >
> > > No sense having 8 or 16 reply queues if you only have 4 cpus,
> > > and likewise no sense limiting to 8 reply queues if you have
> > > many more cpus.
> >
> > I've applied this as it looks good as-is, but shouldn't we also
> > cap the number of MSI-X vectors in common code so that we avoid
> > adding this as boilerplate code to lots of drivers?
>
> Maybe so. Thinking about CPU hotplug, is num_online_cpus()
> the right cap? Maybe num_possible_cpus() is better in case
> additional cpus coming online are anticipated?
On second thought, might there be PCI devices which have multiple
MSIX vectors to signal different things? I know for smart array
the idea has occasionally been floated to have an additional vector
to signal something to the host that is not a command completion,
although we never implemented such a thing. Had we done so,
we would then need num_online_cpus() + 1 vectors.
So maybe it's not a good idea to put such a limit in the generic
pci code in case some device works in such a way.
-- steve
>
> >
> > >
> > > Signed-off-by: Stephen M. Cameron <scame...@beardog.cce.hp.com>
> > > Reviewed-by: Mike Miller <michael.mil...@canonical.com>
> > > Reviewed-by: Scott Teel <scott.t...@hp.com>
> > > ---
> > > drivers/scsi/hpsa.c | 2 ++
> > > drivers/scsi/hpsa_cmd.h | 2 +-
> > > 2 files changed, 3 insertions(+), 1 deletions(-)
> > >
> > > diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c
> > > index b1ecfd8..b903e86 100644
> > > --- a/drivers/scsi/hpsa.c
> > > +++ b/drivers/scsi/hpsa.c
> > > @@ -6157,6 +6157,8 @@ static void hpsa_interrupt_mode(struct ctlr_info *h)
> > > if (pci_find_capability(h->pdev, PCI_CAP_ID_MSIX)) {
> > > dev_info(&h->pdev->dev, "MSIX\n");
> > > h->msix_vector = MAX_REPLY_QUEUES;
> > > + if (h->msix_vector > num_online_cpus())
> > > + h->msix_vector = num_online_cpus();
> > > err = pci_enable_msix(h->pdev, hpsa_msix_entries,
> > > h->msix_vector);
> > > if (err > 0) {
> > > diff --git a/drivers/scsi/hpsa_cmd.h b/drivers/scsi/hpsa_cmd.h
> > > index db89245..104b67b 100644
> > > --- a/drivers/scsi/hpsa_cmd.h
> > > +++ b/drivers/scsi/hpsa_cmd.h
> > > @@ -615,7 +615,7 @@ struct TransTable_struct {
> > > u32 RepQCount;
> > > u32 RepQCtrAddrLow32;
> > > u32 RepQCtrAddrHigh32;
> > > -#define MAX_REPLY_QUEUES 8
> > > +#define MAX_REPLY_QUEUES 64
> > > struct vals32 RepQAddr[MAX_REPLY_QUEUES];
> > > };
> > >
> > >
> > > --
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> > ---end quoted text---
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