From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Now that the avc locking is batched move the freeing of AVCs
outside the lock. This lowers lock contention somewhat more on
a fork/exit intensive workload.
Acked-by: Rik van Riel<riel@xxxxxxxxxx>
Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
---
mm/rmap.c | 24 ++++++++++++++----------
1 files changed, 14 insertions(+), 10 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index d4d3680..57f8ba9 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -302,7 +302,6 @@ static void anon_vma_unlink(struct anon_vma_chain *anon_vma_chain,
struct anon_vma_lock_state *avs)
{
struct anon_vma *anon_vma = anon_vma_chain->anon_vma;
- int empty;
/* If anon_vma_fork fails, we can get an empty anon_vma_chain. */
if (!anon_vma)
@@ -310,19 +309,14 @@ static void anon_vma_unlink(struct anon_vma_chain *anon_vma_chain,
anon_vma_lock_batch(anon_vma, avs);
list_del(&anon_vma_chain->same_anon_vma);
-
- /* We must garbage collect the anon_vma if it's empty */
- empty = list_empty(&anon_vma->head);
-
- if (empty)
- put_anon_vma(anon_vma);
}
void unlink_anon_vmas(struct vm_area_struct *vma)
{
struct anon_vma_chain *avc, *next;
struct anon_vma_lock_state avs;
-
+ LIST_HEAD(avmas);
+
/*
* Unlink each anon_vma chained to the VMA. This list is ordered
* from newest to oldest, ensuring the root anon_vma gets freed last.
@@ -330,10 +324,20 @@ void unlink_anon_vmas(struct vm_area_struct *vma)
anon_vma_lock_batch_init(&avs);
list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
anon_vma_unlink(avc, &avs);
- list_del(&avc->same_vma);
- anon_vma_chain_free(avc);
+ list_move(&avc->same_vma, &avmas);
}
anon_vma_unlock_batch(&avs);
+
+ /* Now free them outside the lock */
+ list_for_each_entry_safe(avc, next, &avmas, same_vma) {
+ /*
+ * list_empty check can be done lockless because
+ * once it is empty noone will readd.
+ */
+ if (list_empty(&avc->anon_vma->head))
+ put_anon_vma(avc->anon_vma);
+ anon_vma_chain_free(avc);
+ }
}
static void anon_vma_ctor(void *data)
--
1.7.4.4
--
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