From c5e6688752c25434d71920bc969f9fab60353c5e Mon Sep 17 00:00:00 2001 From: Alex Williamson Date: Fri, 6 Feb 2015 14:19:12 -0700 Subject: [PATCH] vfio/type1: Add conditional rescheduling IOMMU operations can be expensive and it's not very difficult for a user to give us a lot of work to do for a map or unmap operation. Killing a large VM will vfio assigned devices can result in soft lockups and IOMMU tracing shows that we can easily spend 80% of our time with need-resched set. A sprinkling of conf_resched() calls after map and unmap calls has a very tiny affect on performance while resulting in traces with <1% of calls overflowing into needs- resched. Signed-off-by: Alex Williamson --- drivers/vfio/vfio_iommu_type1.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c index 35c90089478e..57d8c37a002b 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -351,8 +351,10 @@ static void vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma) domain = d = list_first_entry(&iommu->domain_list, struct vfio_domain, next); - list_for_each_entry_continue(d, &iommu->domain_list, next) + list_for_each_entry_continue(d, &iommu->domain_list, next) { iommu_unmap(d->domain, dma->iova, dma->size); + cond_resched(); + } while (iova < end) { size_t unmapped, len; @@ -384,6 +386,8 @@ static void vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma) unmapped >> PAGE_SHIFT, dma->prot, false); iova += unmapped; + + cond_resched(); } vfio_lock_acct(-unlocked); @@ -528,6 +532,8 @@ static int vfio_iommu_map(struct vfio_iommu *iommu, dma_addr_t iova, map_try_harder(d, iova, pfn, npage, prot)) goto unwind; } + + cond_resched(); } return 0; -- 2.20.1