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Date: Tue, 19 May 2015 10:20:47 +0000 From: Joao Martins <Joao.Martins@...lab.eu> To: David Vrabel <david.vrabel@...rix.com>, "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org> CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>, "wei.liu2@...rix.com" <wei.liu2@...rix.com>, "ian.campbell@...rix.com" <ian.campbell@...rix.com>, "boris.ostrovsky@...cle.com" <boris.ostrovsky@...cle.com> Subject: Re: [Xen-devel] [RFC PATCH 12/13] xen-netfront: implement TX persistent grants On 18 May 2015, at 17:55, David Vrabel <david.vrabel@...rix.com> wrote: > On 12/05/15 18:18, Joao Martins wrote: >> Instead of grant/revoking the buffer related to the skb, it will use >> an already granted page and memcpy to it. The grants will be mapped >> by xen-netback and reused overtime, but only unmapped when the vif >> disconnects, as opposed to every packet. >> >> This only happens if the backend supports persistent grants since it >> would, otherwise, introduce the overhead of a memcpy on top of the >> grant map. > [...] >> --- a/drivers/net/xen-netfront.c >> +++ b/drivers/net/xen-netfront.c > [...] >> @@ -1610,7 +1622,10 @@ static int xennet_init_queue(struct netfront_queue *queue) >> for (i = 0; i < NET_TX_RING_SIZE; i++) { >> skb_entry_set_link(&queue->tx_skbs[i], i+1); >> queue->grant_tx[i].ref = GRANT_INVALID_REF; >> - queue->grant_tx[i].page = NULL; >> + if (queue->info->feature_persistent) >> + queue->grant_tx[i].page = alloc_page(GFP_NOIO); > > Need to check for alloc failure here and unwind correctly? Sorry, I overlooked this check. I will fix that. > Why NOIO? May be I am misusing NOIO where I meant __GFP_WAIT. Tough given we are under rtnl_lock() perhaps GFP_ATOMIC should be used instead.-- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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