From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f174.google.com (mail-io0-f174.google.com [209.85.223.174]) by kanga.kvack.org (Postfix) with ESMTP id A66036B0256 for ; Fri, 4 Sep 2015 13:01:09 -0400 (EDT) Received: by iofb144 with SMTP id b144so30846311iof.1 for ; Fri, 04 Sep 2015 10:01:09 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id na7si456183pdb.93.2015.09.04.10.01.08 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 04 Sep 2015 10:01:09 -0700 (PDT) Subject: [RFC PATCH 2/3] net: NIC helper API for building array of skbs to free From: Jesper Dangaard Brouer Date: Fri, 04 Sep 2015 19:01:06 +0200 Message-ID: <20150904170104.4312.47707.stgit@devil> In-Reply-To: <20150904165944.4312.32435.stgit@devil> References: <20150904165944.4312.32435.stgit@devil> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: netdev@vger.kernel.org, akpm@linux-foundation.org Cc: linux-mm@kvack.org, Jesper Dangaard Brouer , aravinda@linux.vnet.ibm.com, Christoph Lameter , "Paul E. McKenney" , iamjoonsoo.kim@lge.com The NIC device drivers are expected to use this small helper API, when building up an array of objects/skbs to bulk free, while (loop) processing objects to free. Objects to be free'ed later is added (dev_free_waitlist_add) to an array and flushed if the array runs full. After processing the array is flushed (dev_free_waitlist_flush). The array should be stored on the local stack. Usage e.g. during TX completion loop the NIC driver can replace dev_consume_skb_any() with an "add" and after the loop a "flush". For performance reasons the compiler should inline most of these functions. Signed-off-by: Jesper Dangaard Brouer --- include/linux/netdevice.h | 62 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 05b9a694e213..d0133e778314 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -2935,6 +2935,68 @@ static inline void dev_consume_skb_any(struct sk_buff *skb) __dev_kfree_skb_any(skb, SKB_REASON_CONSUMED); } +/* The NIC device drivers are expected to use this small helper API, + * when building up an array of objects/skbs to bulk free, while + * (loop) processing objects to free. Objects to be free'ed later is + * added (dev_free_waitlist_add) to an array and flushed if the array + * runs full. After processing the array is flushed (dev_free_waitlist_flush). + * The array should be stored on the local stack. + * + * Usage e.g. during TX completion loop the NIC driver can replace + * dev_consume_skb_any() with an "add" and after the loop a "flush". + * + * For performance reasons the compiler should inline most of these + * functions. + */ +struct dev_free_waitlist { + struct sk_buff **skbs; + unsigned int skb_cnt; +}; + +static void __dev_free_waitlist_bulkfree(struct dev_free_waitlist *wl) +{ + /* Cannot bulk free from interrupt context or with IRQs + * disabled, due to how SLAB bulk API works (and gain it's + * speedup). This can e.g. happen due to invocation from + * netconsole/netpoll. + */ + if (unlikely(in_irq() || irqs_disabled())) { + int i; + + for (i = 0; i < wl->skb_cnt; i++) + dev_consume_skb_irq(wl->skbs[i]); + } else { + /* Likely fastpath, don't call with cnt == 0 */ + kfree_skb_bulk(wl->skbs, wl->skb_cnt); + } +} + +static inline void dev_free_waitlist_flush(struct dev_free_waitlist *wl) +{ + /* Flush the waitlist, but only if any objects remain, as bulk + * freeing "zero" objects is not supported and plus it avoids + * pointless function calls. + */ + if (likely(wl->skb_cnt)) + __dev_free_waitlist_bulkfree(wl); +} + +static __always_inline void dev_free_waitlist_add(struct dev_free_waitlist *wl, + struct sk_buff *skb, + unsigned int max) +{ + /* It is recommended that max is a builtin constant, as this + * saves one register when inlined. Catch offenders with: + * BUILD_BUG_ON(!__builtin_constant_p(max)); + */ + wl->skbs[wl->skb_cnt++] = skb; + if (wl->skb_cnt == max) { + /* Detect when waitlist array is full, then flush and reset */ + __dev_free_waitlist_bulkfree(wl); + wl->skb_cnt = 0; + } +} + int netif_rx(struct sk_buff *skb); int netif_rx_ni(struct sk_buff *skb); int netif_receive_skb_sk(struct sock *sk, struct sk_buff *skb); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org