Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1945994AbbEWDze (ORCPT ); Fri, 22 May 2015 23:55:34 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:42366 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1422663AbbEWDza (ORCPT ); Fri, 22 May 2015 23:55:30 -0400 From: Mike Kravetz To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Naoya Horiguchi , Davidlohr Bueso , David Rientjes , Luiz Capitulino , Andrew Morton , Mike Kravetz Subject: [PATCH v2 1/2] mm/hugetlb: compute/return the number of regions added by region_add() Date: Fri, 22 May 2015 20:55:03 -0700 Message-Id: <1432353304-12767-2-git-send-email-mike.kravetz@oracle.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1432353304-12767-1-git-send-email-mike.kravetz@oracle.com> References: <1432353304-12767-1-git-send-email-mike.kravetz@oracle.com> X-Source-IP: userv0022.oracle.com [156.151.31.74] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8079 Lines: 222 Modify region_add() to keep track of regions(pages) added to the reserve map and return this value. The return value can be compared to the return value of region_chg() to determine if the map was modified between calls. Add documentation to the reserve/region map routines. Make vma_commit_reservation() also pass along the return value of region_add(). In the normal case, we want vma_commit_reservation to return the same value as the preceding call to vma_needs_reservation. Create a common __vma_reservation_common routine to help keep the special case return values in sync Signed-off-by: Mike Kravetz --- mm/hugetlb.c | 120 ++++++++++++++++++++++++++++++++++++++++++++++------------- 1 file changed, 94 insertions(+), 26 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 54f129d..3855889 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -212,8 +212,16 @@ static inline struct hugepage_subpool *subpool_vma(struct vm_area_struct *vma) * Region tracking -- allows tracking of reservations and instantiated pages * across the pages in a mapping. * - * The region data structures are embedded into a resv_map and - * protected by a resv_map's lock + * The region data structures are embedded into a resv_map and protected + * by a resv_map's lock. The set of regions within the resv_map represent + * reservations for huge pages, or huge pages that have already been + * instantiated within the map. The from and to elements are huge page + * indicies into the associated mapping. from indicates the starting index + * of the region. to represents the first index past the end of the region. + * For example, a file region structure with from == 0 and to == 4 represents + * four huge pages in a mapping. It is important to note that the to element + * represents the first element past the end of the region. This is used in + * arithmetic as 4(to) - 0(from) = 4 huge pages in the region. */ struct file_region { struct list_head link; @@ -221,10 +229,23 @@ struct file_region { long to; }; +/* + * Add the huge page range represented by indicies f (from) + * and t (to) to the reserve map. Existing regions will be + * expanded to accommodate the specified range. We know only + * existing regions need to be expanded, because region_add + * is only called after region_chg(with the same range). If + * a new file_region structure must be allocated, it is done + * in region_chg. + * + * Return the number of new huge pages added to the map. This + * number is greater than or equal to zero. + */ static long region_add(struct resv_map *resv, long f, long t) { struct list_head *head = &resv->regions; struct file_region *rg, *nrg, *trg; + long add = 0; spin_lock(&resv->lock); /* Locate the region we are either in or before. */ @@ -250,16 +271,44 @@ static long region_add(struct resv_map *resv, long f, long t) if (rg->to > t) t = rg->to; if (rg != nrg) { + /* Decrement return value by the deleted range. + * Another range will span this area so that by + * end of routine add will be >= zero + */ + add -= (rg->to - rg->from); list_del(&rg->link); kfree(rg); } } + + add += (nrg->from - f); /* Added to beginning of region */ nrg->from = f; + add += t - nrg->to; /* Added to end of region */ nrg->to = t; + spin_unlock(&resv->lock); - return 0; + return add; } +/* + * Examine the existing reserve map and determine how many + * huge pages in the specified range (f, t) are NOT currently + * represented. This routine is called before a subsequent + * call to region_add that will actually modify the reserve + * map to add the specified range (f, t). region_chg does + * not change the number of huge pages represented by the + * map. However, if the existing regions in the map can not + * be expanded to represent the new range, a new file_region + * structure is added to the map as a placeholder. This is + * so that the subsequent region_add call will have all + * regions it needs and will not fail. + * + * Returns the number of huge pages that need to be added + * to the existing reservation map for the range (f, t). + * This number is greater or equal to zero. -ENOMEM is + * returned if a new file_region structure can not be + * allocated. + */ static long region_chg(struct resv_map *resv, long f, long t) { struct list_head *head = &resv->regions; @@ -326,6 +375,11 @@ out_nrg: return chg; } +/* + * Truncate the reserve map at index 'end'. Modify/truncate any + * region which contains end. Delete any regions past end. + * Return the number of huge pages removed from the map. + */ static long region_truncate(struct resv_map *resv, long end) { struct list_head *head = &resv->regions; @@ -361,6 +415,10 @@ out: return chg; } +/* + * Count and return the number of huge pages in the reserve map + * that intersect with the range (f, t). + */ static long region_count(struct resv_map *resv, long f, long t) { struct list_head *head = &resv->regions; @@ -1424,46 +1482,56 @@ static void return_unused_surplus_pages(struct hstate *h, } /* - * Determine if the huge page at addr within the vma has an associated - * reservation. Where it does not we will need to logically increase - * reservation and actually increase subpool usage before an allocation - * can occur. Where any new reservation would be required the - * reservation change is prepared, but not committed. Once the page - * has been allocated from the subpool and instantiated the change should - * be committed via vma_commit_reservation. No action is required on - * failure. + * vma_needs_reservation and vma_commit_reservation are used by the huge + * page allocation routines to manage reservations. + * + * vma_needs_reservation is called to determine if the huge page at addr + * within the vma has an associated reservation. If a reservation is + * needed, the value 1 is returned. The caller is then responsible for + * managing the global reservation and subpool usage counts. After + * the huge page has been allocated, vma_commit_reservation is called + * to add the page to the reservation map. + * + * In the normal case, vma_commit_reservation should return the same value + * as the preceding vma_needs_reservation call. The only time this is + * not the case is if a reserve map was changed between calls. It is the + * responsibility of the caller to notice the difference and take appropriate + * action. */ -static long vma_needs_reservation(struct hstate *h, - struct vm_area_struct *vma, unsigned long addr) +static long __vma_reservation_common(struct hstate *h, + struct vm_area_struct *vma, unsigned long addr, + bool needs) { struct resv_map *resv; pgoff_t idx; - long chg; + long ret; resv = vma_resv_map(vma); if (!resv) return 1; idx = vma_hugecache_offset(h, vma, addr); - chg = region_chg(resv, idx, idx + 1); + if (needs) + ret = region_chg(resv, idx, idx + 1); + else + ret = region_add(resv, idx, idx + 1); if (vma->vm_flags & VM_MAYSHARE) - return chg; + return ret; else - return chg < 0 ? chg : 0; + return ret < 0 ? ret : 0; } -static void vma_commit_reservation(struct hstate *h, + +static long vma_needs_reservation(struct hstate *h, struct vm_area_struct *vma, unsigned long addr) { - struct resv_map *resv; - pgoff_t idx; - - resv = vma_resv_map(vma); - if (!resv) - return; + return __vma_reservation_common(h, vma, addr, (bool)1); +} - idx = vma_hugecache_offset(h, vma, addr); - region_add(resv, idx, idx + 1); +static long vma_commit_reservation(struct hstate *h, + struct vm_area_struct *vma, unsigned long addr) +{ + return __vma_reservation_common(h, vma, addr, (bool)0); } static struct page *alloc_huge_page(struct vm_area_struct *vma, -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/