From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by huchra.bufferbloat.net (Postfix, from userid 1000) id CE87221F0F2; Mon, 31 Dec 2012 10:08:21 -0800 (PST) From: =?UTF-8?q?Dave=20T=C3=A4ht?= To: edumazet@google.com, cerowrt-devel@lists.bufferbloat.net Date: Mon, 31 Dec 2012 10:08:05 -0800 Message-Id: <1356977285-12964-1-git-send-email-dave.taht@bufferbloat.net> X-Mailer: git-send-email 1.7.1 Subject: [Cerowrt-devel] [PATCH] skb_reduce_truesize: helper function for shrinking skbs whenever needed X-BeenThere: cerowrt-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: Development issues regarding the cerowrt test router project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 31 Dec 2012 18:08:21 -0000 From: Dave Taht On embedded devices in particular, large queues of small packets from the rx path with a large truesize can exist. Reducing their size can reduce memory pressure. skb_reduce_truesize is a helper function for doing this, when needed. --- include/linux/skbuff.h | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 6a2c34e..2080cb1 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1671,6 +1671,24 @@ static inline void pskb_trim_unique(struct sk_buff *skb, unsigned int len) BUG_ON(err); } +/* + * Caller wants to reduce memory needs before queueing skb + * The (expensive) copy should not be be done in fast path. + */ +static inline struct sk_buff *skb_reduce_truesize(struct sk_buff *skb) +{ + if (skb->truesize > 2 * SKB_TRUESIZE(skb->len)) { + struct sk_buff *nskb; + nskb = skb_copy_expand(skb, skb_headroom(skb), 0, + GFP_ATOMIC | __GFP_NOWARN); + if (nskb) { + __kfree_skb(skb); + skb = nskb; + } + } + return skb; +} + /** * skb_orphan - orphan a buffer * @skb: buffer to orphan -- 1.7.9.5