Re: [PATCH 03/15] powerpc/msi: Improve IRQ bitmap allocator

Scott Wood
2014-09-22T23:50:59Z

On Mon, 2014-09-22 at 11:26 +0300, Laurentiu Tudor wrote:
> On 09/19/2014 11:19 PM, Scott Wood wrote:
> > On Fri, 2014-09-19 at 15:16 -0500, Scott Wood wrote:
> >> On Thu, 2014-09-18 at 18:26 +1000, Michael Neuling wrote:
> >>> From: Ian Munsie <imunsie@au1.ibm.com>
> >>>
> >>> Currently msi_bitmap_alloc_hwirqs() will round up any IRQ allocation requests
> >>> to the nearest power of 2. eg. ask for 5 IRQs and you'll get 8. This wastes a
> >>> lot of IRQs which can be a scarce resource.
> >>>
> >>> For cxl we can require multiple IRQs for every contexts that is attached to the
> >>> accelerator. For AFU directed accelerators, there may be 1000s of contexts
> >>> attached, hence we can easily run out of IRQs, especially if we are needlessly
> >>> wasting them.
> >>>
> >>> This changes the msi_bitmap_alloc_hwirqs() to allocate only the required number
> >>> of IRQs, hence avoiding this wastage.
> >>>
> >>> Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
> >>> Signed-off-by: Michael Neuling <mikey@neuling.org>
> >>> ---
> >>> arch/powerpc/sysdev/msi_bitmap.c | 18 +++++++++++++-----
> >>> 1 file changed, 13 insertions(+), 5 deletions(-)
> >>
> >> This conflicts with (and partially duplicates)
> >> http://patchwork.ozlabs.org/patch/381892/
> >> which I have in my tree. How should we handle it?
> >>
> >> Laurentiu, from looking at the overlap between patches I see a problem
> >> with your existing patch, regarding the out-of-irqs path and
> >> msi_bitmap_free_hwirqs(), so one way or another that needs to get fixed
> >> soon.
> >
> > Given the problems with Laurentiu's patch, perhaps it'd be best for me
> > to just revert that patch in my tree, and respin it after this patchset
> > has been merged.
>
> Let me know if you want me to rebase my stuff on top of Michael's patch.

Yes, please resend it once Michael's patch gets merged.

-Scott