[PATCH 13/26] mm: reclaim_state records pages reclaimed, not slabs

Dave Chinner
2019-10-09T03:21:51Z

From: Dave Chinner <dchinner@redhat.com>

Add a wrapper to account for page freeing in shrinker reclaim so
that the high level scanning accounts for all the memory freed
during a shrinker scan.

No logic changes, just replacing open coded checks with a simple
wrapper.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
fs/inode.c | 3 +--
fs/xfs/xfs_buf.c | 4 +---
include/linux/swap.h | 20 ++++++++++++++++++--
mm/slab.c | 3 +--
mm/slob.c | 4 +---
mm/slub.c | 3 +--
mm/vmscan.c | 4 ++--
7 files changed, 25 insertions(+), 16 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index fef457a42882..a77caf216659 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -764,8 +764,7 @@ static enum lru_status inode_lru_isolate(struct list_head *item,
__count_vm_events(KSWAPD_INODESTEAL, reap);
else
__count_vm_events(PGINODESTEAL, reap);
- if (current->reclaim_state)
- current->reclaim_state->reclaimed_slab += reap;
+ current_reclaim_account_pages(reap);
}
iput(inode);
spin_lock(lru_lock);
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 45b470f55ad7..bc5e0c712e2e 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -324,9 +324,7 @@ xfs_buf_free(

__free_page(page);
}
- if (current->reclaim_state)
- current->reclaim_state->reclaimed_slab +=
- bp->b_page_count;
+ current_reclaim_account_pages(bp->b_page_count);
} else if (bp->b_flags & _XBF_KMEM)
kmem_free(bp->b_addr);
_xfs_buf_free_pages(bp);
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 063c0c1e112b..72b855fe20b0 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -126,12 +126,28 @@ union swap_header {

/*
* current->reclaim_state points to one of these when a task is running
- * memory reclaim
+ * memory reclaim. It is typically used by shrinkers to return reclaim
+ * information back to the main vmscan loop.
*/
struct reclaim_state {
- unsigned long reclaimed_slab;
+ unsigned long reclaimed_pages; /* pages freed by shrinkers */
};

+/*
+ * When code frees a page that may be run from a memory reclaim context, it
+ * needs to account for the pages it frees so memory reclaim can track them.
+ * Slab memory that is freed is accounted via this mechanism, so this is not
+ * necessary for slab or heap memory being freed. However, if the object being
+ * freed frees pages directly, then those pages should be accounted as well when
+ * in memory reclaim. This helper function takes care accounting for the pages
+ * being reclaimed when it is required.
+ */
+static inline void current_reclaim_account_pages(int nr_pages)
+{
+ if (current->reclaim_state)
+ current->reclaim_state->reclaimed_pages += nr_pages;
+}
+
#ifdef __KERNEL__

struct address_space;
diff --git a/mm/slab.c b/mm/slab.c
index 9df370558e5d..05baeda97fef 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1395,8 +1395,7 @@ static void kmem_freepages(struct kmem_cache *cachep, struct page *page)
page_mapcount_reset(page);
page->mapping = NULL;

- if (current->reclaim_state)
- current->reclaim_state->reclaimed_slab += 1 << order;
+ current_reclaim_account_pages(1 << order);
uncharge_slab_page(page, order, cachep);
__free_pages(page, order);
}
diff --git a/mm/slob.c b/mm/slob.c
index fa53e9f73893..c54a7eeee86d 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -211,9 +211,7 @@ static void slob_free_pages(void *b, int order)
{
struct page *sp = virt_to_page(b);

- if (current->reclaim_state)
- current->reclaim_state->reclaimed_slab += 1 << order;
-
+ current_reclaim_account_pages(1 << order);
mod_node_page_state(page_pgdat(sp), NR_SLAB_UNRECLAIMABLE,
-(1 << order));
__free_pages(sp, order);
diff --git a/mm/slub.c b/mm/slub.c
index 3d63ae320d31..c79122dd9452 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1746,8 +1746,7 @@ static void __free_slab(struct kmem_cache *s, struct page *page)
__ClearPageSlab(page);

page->mapping = NULL;
- if (current->reclaim_state)
- current->reclaim_state->reclaimed_slab += pages;
+ current_reclaim_account_pages(pages);
uncharge_slab_page(page, order, s);
__free_pages(page, order);
}
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 65093dd89dd7..feea179bcb67 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2872,8 +2872,8 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
} while ((memcg = mem_cgroup_iter(root, memcg, NULL)));

if (reclaim_state) {
- sc->nr_reclaimed += reclaim_state->reclaimed_slab;
- reclaim_state->reclaimed_slab = 0;
+ sc->nr_reclaimed += reclaim_state->reclaimed_pages;
+ reclaim_state->reclaimed_pages = 0;
}

/* Record the subtree's reclaim efficiency */
--
2.23.0.rc1