Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752838AbaLDC4K (ORCPT ); Wed, 3 Dec 2014 21:56:10 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51707 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752027AbaLDC4I (ORCPT ); Wed, 3 Dec 2014 21:56:08 -0500 Date: Thu, 04 Dec 2014 03:03:34 +0008 From: Jason Wang Subject: Re: [PATCH v3 net-next 2/2 tuntap: Increase the number of queues in tun. To: "Michael S. Tsirkin" Cc: Pankaj Gupta , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, davem@davemloft.net, dgibson@redhat.com, vfalico@gmail.com, edumazet@google.com, vyasevic@redhat.com, hkchu@google.com, wuzhy@linux.vnet.ibm.com, xemul@parallels.com, therbert@google.com, bhutchings@solarflare.com, xii@google.com, stephen@networkplumber.org, jiri@resnulli.us, sergei.shtylyov@cogentembedded.com Message-Id: <1417661734.16500.0@smtp.corp.redhat.com> In-Reply-To: <20141203095210.GC9487@redhat.com> References: <1417591177-7985-1-git-send-email-pagupta@redhat.com> <1417591177-7985-3-git-send-email-pagupta@redhat.com> <20141203095210.GC9487@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 3, 2014 at 5:52 PM, Michael S. Tsirkin wrote: > On Wed, Dec 03, 2014 at 12:49:37PM +0530, Pankaj Gupta wrote: >> Networking under kvm works best if we allocate a per-vCPU RX and TX >> queue in a virtual NIC. This requires a per-vCPU queue on the host >> side. >> >> It is now safe to increase the maximum number of queues. >> Preceding patche: 'net: allow large number of rx queues' > > s/patche/patch/ > >> made sure this won't cause failures due to high order memory >> allocations. Increase it to 256: this is the max number of vCPUs >> KVM supports. >> >> Signed-off-by: Pankaj Gupta >> Reviewed-by: David Gibson > > Hmm it's kind of nasty that each tun device is now using x16 memory. > Maybe we should look at using a flex array instead, and removing the > limitation altogether (e.g. make it INT_MAX)? But this only happens when IFF_MULTIQUEUE were used. And core has vmalloc() fallback. So probably not a big issue? > > > >> --- >> drivers/net/tun.c | 9 +++++---- >> 1 file changed, 5 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/net/tun.c b/drivers/net/tun.c >> index e3fa65a..a19dc5f8 100644 >> --- a/drivers/net/tun.c >> +++ b/drivers/net/tun.c >> @@ -113,10 +113,11 @@ struct tap_filter { >> unsigned char addr[FLT_EXACT_COUNT][ETH_ALEN]; >> }; >> >> -/* DEFAULT_MAX_NUM_RSS_QUEUES were chosen to let the rx/tx queues >> allocated for >> - * the netdevice to be fit in one page. So we can make sure the >> success of >> - * memory allocation. TODO: increase the limit. */ >> -#define MAX_TAP_QUEUES DEFAULT_MAX_NUM_RSS_QUEUES >> +/* MAX_TAP_QUEUES 256 is chosen to allow rx/tx queues to be equal >> + * to max number of vCPUS in guest. Also, we are making sure here >> + * queue memory allocation do not fail. > > It's not queue memory allocation anymore, is it? > I would say " > This also helps the tfiles field fit in 4K, so the whole tun > device only needs an order-1 allocation. > " > >> + */ >> +#define MAX_TAP_QUEUES 256 >> #define MAX_TAP_FLOWS 4096 >> >> #define TUN_FLOW_EXPIRE (3 * HZ) >> -- >> 1.8.3.1 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe netdev" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html -- 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/