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[3.13.y-ckt,stable] Patch "net: don't wait for order-3 page allocation" has been added to staging queue

Message ID 1436829252-24457-1-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa July 13, 2015, 11:14 p.m. UTC 
This is a note to let you know that I have just added a patch titled

    net: don't wait for order-3 page allocation

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt24.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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From 232378347b5ca13f3c92db02b07677cd62feffd6 Mon Sep 17 00:00:00 2001
From: Shaohua Li <shli@fb.com>
Date: Thu, 11 Jun 2015 16:50:48 -0700
Subject: net: don't wait for order-3 page allocation

[ 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@google.com>
Cc: Chris Mason <clm@fb.com>
Cc: Debabrata Banerjee <dbavatar@gmail.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 net/core/skbuff.c | 4 +++-
 net/core/sock.c   | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

--
1.9.1
diff mbox

Patch

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index a937b23..1216c57 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -366,9 +366,11 @@  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 8235166..fa5f321 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1938,8 +1938,10 @@  bool skb_page_frag_refill(unsigned int sz, struct page_frag *pfrag, gfp_t prio)
 	do {
 		gfp_t gfp = prio;

-		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;