Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752849AbaGQEoA (ORCPT ); Thu, 17 Jul 2014 00:44:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:20207 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750832AbaGQEn5 (ORCPT ); Thu, 17 Jul 2014 00:43:57 -0400 Message-ID: <53C75481.1090705@redhat.com> Date: Thu, 17 Jul 2014 12:43:45 +0800 From: Jason Wang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Varka Bhadram , rusty@rustcorp.com.au, mst@redhat.com, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org CC: Vlad Yasevich , Eric Dumazet Subject: Re: [PATCH net-next V2 3/3] virtio-net: rx busy polling support References: <1405491707-22706-1-git-send-email-jasowang@redhat.com> <1405491707-22706-4-git-send-email-jasowang@redhat.com> <53C63A11.4050401@gmail.com> <53C73B29.4070107@redhat.com> <53C742BA.3050402@gmail.com> In-Reply-To: <53C742BA.3050402@gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/17/2014 11:27 AM, Varka Bhadram wrote: > > On Thursday 17 July 2014 08:25 AM, Jason Wang wrote: >> On 07/16/2014 04:38 PM, Varka Bhadram wrote: >>> On 07/16/2014 11:51 AM, Jason Wang wrote: >>>> Add basic support for rx busy polling. >>>> >>>> Test was done between a kvm guest and an external host. Two hosts were >>>> connected through 40gb mlx4 cards. With both busy_poll and busy_read >>>> are set to 50 in guest, 1 byte netperf tcp_rr shows 116% improvement: >>>> transaction rate was increased from 9151.94 to 19787.37. >>>> >>>> Cc: Rusty Russell >>>> Cc: Michael S. Tsirkin >>>> Cc: Vlad Yasevich >>>> Cc: Eric Dumazet >>>> Signed-off-by: Jason Wang >>>> --- >>>> drivers/net/virtio_net.c | 190 >>>> ++++++++++++++++++++++++++++++++++++++++++++++- >>>> 1 file changed, 187 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c >>>> index e417d93..4830713 100644 >>>> --- a/drivers/net/virtio_net.c >>>> +++ b/drivers/net/virtio_net.c >>>> @@ -27,6 +27,7 @@ >>>> #include >>>> #include >>>> #include >>>> +#include >>>> static int napi_weight = NAPI_POLL_WEIGHT; >>>> module_param(napi_weight, int, 0444); >>>> @@ -94,8 +95,143 @@ struct receive_queue { >>>> /* Name of this receive queue: input.$index */ >>>> char name[40]; >>>> + >>>> +#ifdef CONFIG_NET_RX_BUSY_POLL >>>> + unsigned int state; >>>> +#define VIRTNET_RQ_STATE_IDLE 0 >>>> +#define VIRTNET_RQ_STATE_NAPI 1 /* NAPI or refill owns >>>> this RQ */ >>>> +#define VIRTNET_RQ_STATE_POLL 2 /* poll owns this RQ */ >>>> +#define VIRTNET_RQ_STATE_DISABLED 4 /* RQ is disabled */ >>>> +#define VIRTNET_RQ_OWNED (VIRTNET_RQ_STATE_NAPI | >>>> VIRTNET_RQ_STATE_POLL) >>>> +#define VIRTNET_RQ_LOCKED (VIRTNET_RQ_OWNED | >>>> VIRTNET_RQ_STATE_DISABLED) >>>> +#define VIRTNET_RQ_STATE_NAPI_YIELD 8 /* NAPI or refill yielded >>>> this RQ */ >>>> +#define VIRTNET_RQ_STATE_POLL_YIELD 16 /* poll yielded this RQ */ >>>> + spinlock_t lock; >>>> +#endif /* CONFIG_NET_RX_BUSY_POLL */ >>>> }; >>>> +#ifdef CONFIG_NET_RX_BUSY_POLL >>>> +static inline void virtnet_rq_init_lock(struct receive_queue *rq) >>>> +{ >>>> + >>>> + spin_lock_init(&rq->lock); >>>> + rq->state = VIRTNET_RQ_STATE_IDLE; >>>> +} >>>> + >>>> +/* called from the device poll routine or refill routine to get >>>> ownership of a >>>> + * receive queue. >>>> + */ >>>> +static inline bool virtnet_rq_lock_napi_refill(struct receive_queue >>>> *rq) >>>> +{ >>>> + int rc = true; >>>> + >>> bool instead of int...? >> Yes, it was better. >>>> + spin_lock(&rq->lock); >>>> + if (rq->state & VIRTNET_RQ_LOCKED) { >>>> + WARN_ON(rq->state & VIRTNET_RQ_STATE_NAPI); >>>> + rq->state |= VIRTNET_RQ_STATE_NAPI_YIELD; >>>> + rc = false; >>>> + } else >>>> + /* we don't care if someone yielded */ >>>> + rq->state = VIRTNET_RQ_STATE_NAPI; >>>> + spin_unlock(&rq->lock); >>> Lock for rq->state ...? >>> >>> If yes: >>> spin_lock(&rq->lock); >>> if (rq->state & VIRTNET_RQ_LOCKED) { >>> rq->state |= VIRTNET_RQ_STATE_NAPI_YIELD; >>> spin_unlock(&rq->lock); >>> WARN_ON(rq->state & VIRTNET_RQ_STATE_NAPI); >>> rc = false; >>> } else { >>> /* we don't care if someone yielded */ >>> rq->state = VIRTNET_RQ_STATE_NAPI; >>> spin_unlock(&rq->lock); >>> } >> I didn't see any differences. Is this used to catch the bug of driver >> earlier? btw, several other rx busy polling capable driver does the same >> thing. > > We need not to include WARN_ON() & rc=false under critical section. > Ok. but unless there's a bug in the driver itself, WARN_ON() should be just a condition check for a branch, so there should not be noticeable differences. Also we should not check rq->state outside the protection of lock. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/