Re: [PATCH 03/15] powerpc/msi: Improve IRQ bitmap allocator
From: Scott Wood <hidden>
Date: 2014-09-19 20:16:34
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On Thu, 2014-09-18 at 18:26 +1000, Michael Neuling wrote:
From: Ian Munsie <redacted> 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 <redacted> Signed-off-by: Michael Neuling <redacted> --- 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. -Scott
quoted hunk ↗ jump to hunk
diff --git a/arch/powerpc/sysdev/msi_bitmap.c b/arch/powerpc/sysdev/msi_bitmap.c index 2ff6302..e001559 100644 --- a/arch/powerpc/sysdev/msi_bitmap.c +++ b/arch/powerpc/sysdev/msi_bitmap.c@@ -24,28 +24,36 @@ int msi_bitmap_alloc_hwirqs(struct msi_bitmap *bmp, int num) * This is fast, but stricter than we need. We might want to add * a fallback routine which does a linear search with no alignment. */ - offset = bitmap_find_free_region(bmp->bitmap, bmp->irq_count, order); + offset = bitmap_find_next_zero_area(bmp->bitmap, bmp->irq_count, 0, + num, (1 << order) - 1); + if (offset > bmp->irq_count) + goto err; + bitmap_set(bmp->bitmap, offset, num); spin_unlock_irqrestore(&bmp->lock, flags); pr_debug("msi_bitmap: allocated 0x%x (2^%d) at offset 0x%x\n", num, order, offset); return offset; +err: + spin_unlock_irqrestore(&bmp->lock, flags); + return -ENOMEM; } +EXPORT_SYMBOL(msi_bitmap_alloc_hwirqs); void msi_bitmap_free_hwirqs(struct msi_bitmap *bmp, unsigned int offset, unsigned int num) { unsigned long flags; - int order = get_count_order(num); - pr_debug("msi_bitmap: freeing 0x%x (2^%d) at offset 0x%x\n", - num, order, offset); + pr_debug("msi_bitmap: freeing 0x%x at offset 0x%x\n", + num, offset); spin_lock_irqsave(&bmp->lock, flags); - bitmap_release_region(bmp->bitmap, offset, order); + bitmap_clear(bmp->bitmap, offset, num); spin_unlock_irqrestore(&bmp->lock, flags); } +EXPORT_SYMBOL(msi_bitmap_free_hwirqs); void msi_bitmap_reserve_hwirq(struct msi_bitmap *bmp, unsigned int hwirq) {