From: Robin Murphy Date: Thu, 28 Sep 2017 10:31:23 +0000 (+0100) Subject: iommu/iova: Try harder to allocate from rcache magazine X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=e8b198402745ed413ed8229b2eb45d34016eb5d8;p=linux.git iommu/iova: Try harder to allocate from rcache magazine When devices with different DMA masks are using the same domain, or for PCI devices where we usually try a speculative 32-bit allocation first, there is a fair possibility that the top PFN of the rcache stack at any given time may be unsuitable for the lower limit, prompting a fallback to allocating anew from the rbtree. Consequently, we may end up artifically increasing pressure on the 32-bit IOVA space as unused IOVAs accumulate lower down in the rcache stacks, while callers with 32-bit masks also impose unnecessary rbtree overhead. In such cases, let's try a bit harder to satisfy the allocation locally first - scanning the whole stack should still be relatively inexpensive. Signed-off-by: Robin Murphy Signed-off-by: Joerg Roedel --- diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c index 15ff3033bbd75..b0ca236820085 100644 --- a/drivers/iommu/iova.c +++ b/drivers/iommu/iova.c @@ -821,12 +821,21 @@ static bool iova_magazine_empty(struct iova_magazine *mag) static unsigned long iova_magazine_pop(struct iova_magazine *mag, unsigned long limit_pfn) { + int i; + unsigned long pfn; + BUG_ON(iova_magazine_empty(mag)); - if (mag->pfns[mag->size - 1] > limit_pfn) - return 0; + /* Only fall back to the rbtree if we have no suitable pfns at all */ + for (i = mag->size - 1; mag->pfns[i] > limit_pfn; i--) + if (i == 0) + return 0; + + /* Swap it to pop it */ + pfn = mag->pfns[i]; + mag->pfns[i] = mag->pfns[--mag->size]; - return mag->pfns[--mag->size]; + return pfn; } static void iova_magazine_push(struct iova_magazine *mag, unsigned long pfn)