[PATCH 11/14] vrange: Purging vrange-anon pages from shrinker

John Stultz
2013-10-03T00:53:43Z

From: Minchan Kim <minchan@kernel.org>

This patch provides the logic to discard anonymous
vranges from the shrinker, by generating the page list
for the volatile ranges setting the ptes volatile, and
discarding the pages.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Android Kernel Team <kernel-team@android.com>
Cc: Robert Love <rlove@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Andrea Righi <andrea@betterlinux.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Mike Hommey <mh@glandium.org>
Cc: Taras Glek <tglek@mozilla.com>
Cc: Dhaval Giani <dhaval.giani@gmail.com>
Cc: Jan Kara <jack@suse.cz>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: linux-mm@kvack.org <linux-mm@kvack.org>
Signed-off-by: Minchan Kim <minchan@kernel.org>
[jstultz: Code tweaks and commit log rewording]
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
mm/vrange.c | 179 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 178 insertions(+), 1 deletion(-)

diff --git a/mm/vrange.c b/mm/vrange.c
index e7c5a25..c6bc32f 100644
--- a/mm/vrange.c
+++ b/mm/vrange.c
@@ -11,6 +11,8 @@
#include <linux/hugetlb.h>
#include "internal.h"
#include <linux/mmu_notifier.h>
+#include <linux/mm_inline.h>
+#include <linux/migrate.h>

static struct kmem_cache *vrange_cachep;

@@ -20,6 +22,11 @@ static struct vrange_list {
struct mutex lock;
} vrange_list;

+struct vrange_walker {
+ struct vm_area_struct *vma;
+ struct list_head *pagelist;
+};
+
static inline unsigned int vrange_size(struct vrange *range)
{
return range->node.last + 1 - range->node.start;
@@ -690,11 +697,181 @@ static struct vrange *vrange_isolate(void)
return vrange;
}

-static unsigned int discard_vrange(struct vrange *vrange)
+static unsigned int discard_vrange_pagelist(struct list_head *page_list)
+{
+ struct page *page;
+ unsigned int nr_discard = 0;
+ LIST_HEAD(ret_pages);
+ LIST_HEAD(free_pages);
+
+ while (!list_empty(page_list)) {
+ int err;
+ page = list_entry(page_list->prev, struct page, lru);
+ list_del(&page->lru);
+ if (!trylock_page(page)) {
+ list_add(&page->lru, &ret_pages);
+ continue;
+ }
+
+ /*
+ * discard_vpage returns unlocked page if it
+ * is successful
+ */
+ err = discard_vpage(page);
+ if (err) {
+ unlock_page(page);
+ list_add(&page->lru, &ret_pages);
+ continue;
+ }
+
+ ClearPageActive(page);
+ list_add(&page->lru, &free_pages);
+ dec_zone_page_state(page, NR_ISOLATED_ANON);
+ nr_discard++;
+ }
+
+ free_hot_cold_page_list(&free_pages, 1);
+ list_splice(&ret_pages, page_list);
+ return nr_discard;
+}
+
+static void vrange_pte_entry(pte_t pteval, unsigned long address,
+ unsigned ptent_size, struct mm_walk *walk)
+{
+ struct page *page;
+ struct vrange_walker *vw = walk->private;
+ struct vm_area_struct *vma = vw->vma;
+ struct list_head *pagelist = vw->pagelist;
+
+ if (pte_none(pteval))
+ return;
+
+ if (!pte_present(pteval))
+ return;
+
+ page = vm_normal_page(vma, address, pteval);
+ if (unlikely(!page))
+ return;
+
+ if (!PageLRU(page) || PageLocked(page))
+ return;
+
+ /* TODO : Support THP */
+ if (unlikely(PageCompound(page)))
+ return;
+
+ if (isolate_lru_page(page))
+ return;
+
+ list_add(&page->lru, pagelist);
+
+ VM_BUG_ON(page_is_file_cache(page));
+ inc_zone_page_state(page, NR_ISOLATED_ANON);
+}
+
+static int vrange_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
+ struct mm_walk *walk)
{
+ pte_t *pte;
+ spinlock_t *ptl;
+
+ pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
+ for (; addr != end; pte++, addr += PAGE_SIZE)
+ vrange_pte_entry(*pte, addr, PAGE_SIZE, walk);
+ pte_unmap_unlock(pte - 1, ptl);
+ cond_resched();
+
return 0;
}

+static unsigned int discard_vma_pages(struct mm_struct *mm,
+ struct vm_area_struct *vma, unsigned long start,
+ unsigned long end)
+{
+ unsigned int ret = 0;
+ LIST_HEAD(pagelist);
+ struct vrange_walker vw;
+ struct mm_walk vrange_walk = {
+ .pmd_entry = vrange_pte_range,
+ .mm = vma->vm_mm,
+ .private = &vw,
+ };
+
+ vw.pagelist = &pagelist;
+ vw.vma = vma;
+
+ walk_page_range(start, end, &vrange_walk);
+
+ if (!list_empty(&pagelist))
+ ret = discard_vrange_pagelist(&pagelist);
+
+ putback_lru_pages(&pagelist);
+ return ret;
+}
+
+/*
+ * vrange->owner isn't stable because caller doesn't hold vrange_lock
+ * so avoid touching vrange->owner.
+ */
+static int __discard_vrange_anon(struct mm_struct *mm, struct vrange *vrange,
+ unsigned int *ret_discard)
+{
+ struct vm_area_struct *vma;
+ unsigned int nr_discard = 0;
+ unsigned long start = vrange->node.start;
+ unsigned long end = vrange->node.last + 1;
+ int ret = 0;
+
+ /* It prevent to destroy vma when the process exist */
+ if (!atomic_inc_not_zero(&mm->mm_users))
+ return ret;
+
+ if (!down_read_trylock(&mm->mmap_sem)) {
+ mmput(mm);
+ ret = -EBUSY;
+ goto out; /* this vrange could be retried */
+ }
+
+ vma = find_vma(mm, start);
+ if (!vma || (vma->vm_start >= end))
+ goto out_unlock;
+
+ for (; vma; vma = vma->vm_next) {
+ if (vma->vm_start >= end)
+ break;
+ BUG_ON(vma->vm_flags & (VM_SPECIAL|VM_LOCKED|VM_MIXEDMAP|
+ VM_HUGETLB));
+ cond_resched();
+ nr_discard += discard_vma_pages(mm, vma,
+ max_t(unsigned long, start, vma->vm_start),
+ min_t(unsigned long, end, vma->vm_end));
+ }
+out_unlock:
+ up_read(&mm->mmap_sem);
+ mmput(mm);
+ *ret_discard = nr_discard;
+out:
+ return ret;
+}
+
+static int discard_vrange(struct vrange *vrange)
+{
+ int ret = 0;
+ struct mm_struct *mm;
+ struct vrange_root *vroot;
+ unsigned int nr_discard = 0;
+ vroot = vrange->owner;
+
+ /* TODO : handle VRANGE_FILE */
+ if (vroot->type != VRANGE_MM)
+ goto out;
+
+ mm = vroot->object;
+ ret = __discard_vrange_anon(mm, vrange, &nr_discard);
+out:
+ return nr_discard;
+}
+
static int shrink_vrange(struct shrinker *s, struct shrink_control *sc)
{
struct vrange *range = NULL;
--
1.8.1.2