From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:46343) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TdR8M-0006BW-JY for qemu-devel@nongnu.org; Tue, 27 Nov 2012 14:48:00 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TdR8G-0007LQ-Ju for qemu-devel@nongnu.org; Tue, 27 Nov 2012 14:47:54 -0500 Received: from mail-ie0-f173.google.com ([209.85.223.173]:34530) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TdR8G-0007KU-D3 for qemu-devel@nongnu.org; Tue, 27 Nov 2012 14:47:48 -0500 Received: by mail-ie0-f173.google.com with SMTP id e13so8323466iej.4 for ; Tue, 27 Nov 2012 11:47:47 -0800 (PST) From: Anthony Liguori In-Reply-To: <20121127162504.GA6210@redhat.com> References: <20121022111824.GA6916@amit.redhat.com> <1350913800.90009.YahooMailClassic@web163904.mail.gq1.yahoo.com> <20121023125503.GG19977@stefanha-thinkpad.redhat.com> <20121101091918.GA19405@amit.redhat.com> <20121101120410.GC3993@redhat.com> <20121101160721.GA9176@redhat.com> <20121127162504.GA6210@redhat.com> Date: Tue, 27 Nov 2012 13:47:43 -0600 Message-ID: <87ip8q6d5s.fsf@codemonkey.ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Subject: Re: [Qemu-devel] [PATCH] virtio: limit avail bytes lookahead List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" , Amit Shah Cc: Stefan Hajnoczi , Bug 1066055 <1066055@bugs.launchpad.net>, qemu-devel@nongnu.org, Edivaldo de Araujo Pereira "Michael S. Tsirkin" writes: > On Thu, Nov 01, 2012 at 06:07:21PM +0200, Michael S. Tsirkin wrote: >> Commit 0d8d7690850eb0cf2b2b60933cf47669a6b6f18f introduced >> a regression in virtio-net performance because it looks >> into the ring aggressively while we really only care >> about a single packet worth of buffers. >> To fix, add parameters limiting lookahead, and >> use in virtqueue_avail_bytes. >> >> Signed-off-by: Michael S. Tsirkin >> Reported-by: Edivaldo de Araujo Pereira > > Ping. > Anthony - going to apply this? Yes, I've got it queued now. In the future, please top post patches. Regards, Anthony Liguori > > >> --- >> >> Edivaldo could you please confirm this fixes regression? >> >> diff --git a/hw/virtio-serial-bus.c b/hw/virtio-serial-bus.c >> index d20bd8b..a761cdc 100644 >> --- a/hw/virtio-serial-bus.c >> +++ b/hw/virtio-serial-bus.c >> @@ -297,7 +297,7 @@ size_t virtio_serial_guest_ready(VirtIOSerialPort *port) >> if (use_multiport(port->vser) && !port->guest_connected) { >> return 0; >> } >> - virtqueue_get_avail_bytes(vq, &bytes, NULL); >> + virtqueue_get_avail_bytes(vq, &bytes, NULL, UINT_MAX, 0); >> return bytes; >> } >> >> diff --git a/hw/virtio.c b/hw/virtio.c >> index ec8b7d8..f40a8c5 100644 >> --- a/hw/virtio.c >> +++ b/hw/virtio.c >> @@ -336,7 +336,8 @@ static unsigned virtqueue_next_desc(hwaddr desc_pa, >> } >> >> void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes, >> - unsigned int *out_bytes) >> + unsigned int *out_bytes, >> + unsigned max_in_bytes, unsigned max_out_bytes) >> { >> unsigned int idx; >> unsigned int total_bufs, in_total, out_total; >> @@ -385,6 +386,9 @@ void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes, >> } else { >> out_total += vring_desc_len(desc_pa, i); >> } >> + if (in_total >= max_in_bytes && out_total >= max_out_bytes) { >> + goto done; >> + } >> } while ((i = virtqueue_next_desc(desc_pa, i, max)) != max); >> >> if (!indirect) >> @@ -392,6 +396,7 @@ void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes, >> else >> total_bufs++; >> } >> +done: >> if (in_bytes) { >> *in_bytes = in_total; >> } >> @@ -405,12 +410,8 @@ int virtqueue_avail_bytes(VirtQueue *vq, unsigned int in_bytes, >> { >> unsigned int in_total, out_total; >> >> - virtqueue_get_avail_bytes(vq, &in_total, &out_total); >> - if ((in_bytes && in_bytes < in_total) >> - || (out_bytes && out_bytes < out_total)) { >> - return 1; >> - } >> - return 0; >> + virtqueue_get_avail_bytes(vq, &in_total, &out_total, in_bytes, out_bytes); >> + return in_bytes <= in_total && out_bytes <= out_total; >> } >> >> void virtqueue_map_sg(struct iovec *sg, hwaddr *addr, >> diff --git a/hw/virtio.h b/hw/virtio.h >> index ac482be..1278328 100644 >> --- a/hw/virtio.h >> +++ b/hw/virtio.h >> @@ -150,7 +150,8 @@ int virtqueue_pop(VirtQueue *vq, VirtQueueElement *elem); >> int virtqueue_avail_bytes(VirtQueue *vq, unsigned int in_bytes, >> unsigned int out_bytes); >> void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes, >> - unsigned int *out_bytes); >> + unsigned int *out_bytes, >> + unsigned max_in_bytes, unsigned max_out_bytes); >> >> void virtio_notify(VirtIODevice *vdev, VirtQueue *vq); >>