From c6a918200c4f4ebf74b7e1ae4fea9115c7b297f8 Mon Sep 17 00:00:00 2001 From: Mike Kravetz Date: Wed, 15 Apr 2015 16:13:36 -0700 Subject: hugetlbfs: add minimum size tracking fields to subpool structure hugetlbfs allocates huge pages from the global pool as needed. Even if the global pool contains a sufficient number pages for the filesystem size at mount time, those global pages could be grabbed for some other use. As a result, filesystem huge page allocations may fail due to lack of pages. Applications such as a database want to use huge pages for performance reasons. hugetlbfs filesystem semantics with ownership and modes work well to manage access to a pool of huge pages. However, the application would like some reasonable assurance that allocations will not fail due to a lack of huge pages. At application startup time, the application would like to configure itself to use a specific number of huge pages. Before starting, the application can check to make sure that enough huge pages exist in the system global pools. However, there are no guarantees that those pages will be available when needed by the application. What the application wants is exclusive use of a subset of huge pages. Add a new hugetlbfs mount option 'min_size=' to indicate that the specified number of pages will be available for use by the filesystem. At mount time, this number of huge pages will be reserved for exclusive use of the filesystem. If there is not a sufficient number of free pages, the mount will fail. As pages are allocated to and freeed from the filesystem, the number of reserved pages is adjusted so that the specified minimum is maintained. This patch (of 4): Add a field to the subpool structure to indicate the minimimum number of huge pages to always be used by this subpool. This minimum count includes allocated pages as well as reserved pages. If the minimum number of pages for the subpool have not been allocated, pages are reserved up to this minimum. An additional field (rsv_hpages) is used to track the number of pages reserved to meet this minimum size. The hstate pointer in the subpool is convenient to have when reserving and unreserving the pages. Signed-off-by: Mike Kravetz Cc: Davidlohr Bueso Cc: Aneesh Kumar Cc: Joonsoo Kim Cc: Andi Kleen Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/hugetlb.h | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 1a782733a420..d1a77b87408d 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -22,7 +22,13 @@ struct mmu_gather; struct hugepage_subpool { spinlock_t lock; long count; - long max_hpages, used_hpages; + long max_hpages; /* Maximum huge pages or -1 if no maximum. */ + long used_hpages; /* Used count against maximum, includes */ + /* both alloced and reserved pages. */ + struct hstate *hstate; + long min_hpages; /* Minimum huge pages or -1 if no minimum. */ + long rsv_hpages; /* Pages reserved against global pool to */ + /* sasitfy minimum size. */ }; struct resv_map { -- cgit v1.2.3