From: Shaohua Li <shli@xxxxxx>
This patch has been added to the 3.12 stable tree. If you have any
objections, please let us know.
===============
[ Upstream commit fb05e7a89f500cfc06ae277bdc911b281928995d ]
We saw excessive direct memory compaction triggered by skb_page_frag_refill.
This causes performance issues and add latency. Commit 5640f7685831e0
introduces the order-3 allocation. According to the changelog, the order-3
allocation isn't a must-have but to improve performance. But direct memory
compaction has high overhead. The benefit of order-3 allocation can't
compensate the overhead of direct memory compaction.
This patch makes the order-3 page allocation atomic. If there is no memory
pressure and memory isn't fragmented, the alloction will still success, so we
don't sacrifice the order-3 benefit here. If the atomic allocation fails,
direct memory compaction will not be triggered, skb_page_frag_refill will
fallback to order-0 immediately, hence the direct memory compaction overhead is
avoided. In the allocation failure case, kswapd is waken up and doing
compaction, so chances are allocation could success next time.
alloc_skb_with_frags is the same.
The mellanox driver does similar thing, if this is accepted, we must fix
the driver too.
V3: fix the same issue in alloc_skb_with_frags as pointed out by Eric
V2: make the changelog clearer
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Chris Mason <clm@xxxxxx>
Cc: Debabrata Banerjee <dbavatar@xxxxxxxxx>
Signed-off-by: Shaohua Li <shli@xxxxxx>
Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
net/core/skbuff.c | 4 +++-
net/core/sock.c | 4 +++-
2 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index fa8448a730a9..b01dd5f421da 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -367,9 +367,11 @@ refill:
for (order = NETDEV_FRAG_PAGE_MAX_ORDER; ;) {
gfp_t gfp = gfp_mask;
- if (order)
+ if (order) {
gfp |= __GFP_COMP | __GFP_NOWARN |
__GFP_NOMEMALLOC;
+ gfp &= ~__GFP_WAIT;
+ }
nc->frag.page = alloc_pages(gfp, order);
if (likely(nc->frag.page))
break;
diff --git a/net/core/sock.c b/net/core/sock.c
index f9ec2f5be1c0..2335a7a130f2 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1907,8 +1907,10 @@ bool sk_page_frag_refill(struct sock *sk, struct page_frag *pfrag)
do {
gfp_t gfp = sk->sk_allocation;
- if (order)
+ if (order) {
gfp |= __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY;
+ gfp &= ~__GFP_WAIT;
+ }
pfrag->page = alloc_pages(gfp, order);
if (likely(pfrag->page)) {
pfrag->offset = 0;
--
2.4.6
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