The branch main has been updated by dougm: URL: https://cgit.FreeBSD.org/src/commit/?id=b831865fe3b8f66281b39a9cb567c92dc285a1da
commit b831865fe3b8f66281b39a9cb567c92dc285a1da Author: Doug Moore <[email protected]> AuthorDate: 2022-06-06 21:26:01 +0000 Commit: Doug Moore <[email protected]> CommitDate: 2022-06-06 21:26:01 +0000 iommu_gas: restrict tree search to promising paths In iommu_gas_lowermatch and iommu_gas_uppermatch, a subtree search is quickly terminated if the largest available free space in the subtree is below a limit, where that limit is related to the size of the allocation request. However, that limit is too small; it does not account for both of the guard pages that will surround the allocated space, but only for one of them. Consequently, it permits the search to proceed through nodes that cannot produce a successful allocation for all the requested space. Fix that limit to improve search performance. Reviewed by: alc, kib Submitted by: Weixi Zhu ([email protected]) MFC after: 3 weeks Differential Revision: https://reviews.freebsd.org/D35414 --- sys/dev/iommu/iommu_gas.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/sys/dev/iommu/iommu_gas.c b/sys/dev/iommu/iommu_gas.c index c0d4f84a3f1c..78dd86c1f255 100644 --- a/sys/dev/iommu/iommu_gas.c +++ b/sys/dev/iommu/iommu_gas.c @@ -384,7 +384,12 @@ iommu_gas_lowermatch(struct iommu_gas_match_args *a, struct iommu_map_entry *ent iommu_gas_match_insert(a); return (0); } - if (entry->free_down < a->size + a->offset + IOMMU_PAGE_SIZE) + + /* + * If the subtree doesn't have free space for the requested allocation + * plus two guard pages, give up. + */ + if (entry->free_down < a->size + a->offset + 2 * IOMMU_PAGE_SIZE) return (ENOMEM); if (entry->first >= a->common->lowaddr) return (ENOMEM); @@ -408,7 +413,11 @@ iommu_gas_uppermatch(struct iommu_gas_match_args *a, struct iommu_map_entry *ent { struct iommu_map_entry *child; - if (entry->free_down < a->size + a->offset + IOMMU_PAGE_SIZE) + /* + * If the subtree doesn't have free space for the requested allocation + * plus two guard pages, give up. + */ + if (entry->free_down < a->size + a->offset + 2 * IOMMU_PAGE_SIZE) return (ENOMEM); if (entry->last < a->common->highaddr) return (ENOMEM);
