From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eugenio =?ISO-8859-1?Q?P=E9rez?= Subject: Re: [PATCH RFC v8 02/11] vhost: use batched get_vq_desc version Date: Mon, 20 Jul 2020 13:16:47 +0200 Message-ID: References: <419cc689-adae-7ba4-fe22-577b3986688c@redhat.com> <0a83aa03-8e3c-1271-82f5-4c07931edea3@redhat.com> <20200709133438-mutt-send-email-mst@kernel.org> <7dec8cc2-152c-83f4-aa45-8ef9c6aca56d@redhat.com> <20200710015615-mutt-send-email-mst@kernel.org> <20200720051410-mutt-send-email-mst@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20200720051410-mutt-send-email-mst@kernel.org> Sender: linux-kernel-owner@vger.kernel.org To: "Michael S. Tsirkin" Cc: Jason Wang , Konrad Rzeszutek Wilk , linux-kernel@vger.kernel.org, kvm list , virtualization@lists.linux-foundation.org, netdev@vger.kernel.org List-Id: virtualization@lists.linuxfoundation.org On Mon, Jul 20, 2020 at 11:27 AM Michael S. Tsirkin wrote: > On Thu, Jul 16, 2020 at 07:16:27PM +0200, Eugenio Perez Martin wrote: > > On Fri, Jul 10, 2020 at 7:58 AM Michael S. Tsirkin wrote: > > > On Fri, Jul 10, 2020 at 07:39:26AM +0200, Eugenio Perez Martin wrote: > > > > > > How about playing with the batch size? Make it a mod parameter instead > > > > > > of the hard coded 64, and measure for all values 1 to 64 ... > > > > > > > > > > Right, according to the test result, 64 seems to be too aggressive in > > > > > the case of TX. > > > > > > > > > > > > > Got it, thanks both! > > > > > > In particular I wonder whether with batch size 1 > > > we get same performance as without batching > > > (would indicate 64 is too aggressive) > > > or not (would indicate one of the code changes > > > affects performance in an unexpected way). > > > > > > -- > > > MST > > > > > > > Hi! > > > > Varying batch_size as drivers/vhost/net.c:VHOST_NET_BATCH, > > sorry this is not what I meant. > > I mean something like this: > > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > index 0b509be8d7b1..b94680e5721d 100644 > --- a/drivers/vhost/net.c > +++ b/drivers/vhost/net.c > @@ -1279,6 +1279,10 @@ static void handle_rx_net(struct vhost_work *work) > handle_rx(net); > } > > +MODULE_PARM_DESC(batch_num, "Number of batched descriptors. (offset from 64)"); > +module_param(batch_num, int, 0644); > +static int batch_num = 0; > + > static int vhost_net_open(struct inode *inode, struct file *f) > { > struct vhost_net *n; > @@ -1333,7 +1337,7 @@ static int vhost_net_open(struct inode *inode, struct file *f) > vhost_net_buf_init(&n->vqs[i].rxq); > } > vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX, > - UIO_MAXIOV + VHOST_NET_BATCH, > + UIO_MAXIOV + VHOST_NET_BATCH + batch_num, > VHOST_NET_PKT_WEIGHT, VHOST_NET_WEIGHT, true, > NULL); > > > then you can try tweaking batching and playing with mod parameter without > recompiling. > > > VHOST_NET_BATCH affects lots of other things. > Ok, got it. Since they were aligned from the start, I thought it was a good idea to maintain them in-sync. > > and testing > > the pps as previous mail says. This means that we have either only > > vhost_net batching (in base testing, like previously to apply this > > patch) or both batching sizes the same. > > > > I've checked that vhost process (and pktgen) goes 100% cpu also. > > > > For tx: Batching decrements always the performance, in all cases. Not > > sure why bufapi made things better the last time. > > > > Batching makes improvements until 64 bufs, I see increments of pps but like 1%. > > > > For rx: Batching always improves performance. It seems that if we > > batch little, bufapi decreases performance, but beyond 64, bufapi is > > much better. The bufapi version keeps improving until I set a batching > > of 1024. So I guess it is super good to have a bunch of buffers to > > receive. > > > > Since with this test I cannot disable event_idx or things like that, > > what would be the next step for testing? > > > > Thanks! > > > > -- > > Results: > > # Buf size: 1,16,32,64,128,256,512 > > > > # Tx > > # === > > # Base > > 2293304.308,3396057.769,3540860.615,3636056.077,3332950.846,3694276.154,3689820 > > # Batch > > 2286723.857,3307191.643,3400346.571,3452527.786,3460766.857,3431042.5,3440722.286 > > # Batch + Bufapi > > 2257970.769,3151268.385,3260150.538,3379383.846,3424028.846,3433384.308,3385635.231,3406554.538 > > > > # Rx > > # == > > # pktgen results (pps) > > 1223275,1668868,1728794,1769261,1808574,1837252,1846436 > > 1456924,1797901,1831234,1868746,1877508,1931598,1936402 > > 1368923,1719716,1794373,1865170,1884803,1916021,1975160 > > > > # Testpmd pps results > > 1222698.143,1670604,1731040.6,1769218,1811206,1839308.75,1848478.75 > > 1450140.5,1799985.75,1834089.75,1871290,1880005.5,1934147.25,1939034 > > 1370621,1721858,1796287.75,1866618.5,1885466.5,1918670.75,1976173.5,1988760.75,1978316 > > > > pktgen was run again for rx with 1024 and 2048 buf size, giving > > 1988760.75 and 1978316 pps. Testpmd goes the same way. > > Don't really understand what does this data mean. > Which number of descs is batched for each run? > Sorry, I should have explained better. I will expand here, but feel free to skip it since we are going to discard the data anyway. Or to propose a better way to tell them. Is a CSV with the values I've obtained, in pps, from pktgen and testpmd. This way is easy to plot them. Maybe is easier as tables, if mail readers/gmail does not misalign them. > > # Tx > > # === Base: With the previous code, not integrating any patch. testpmd is txonly mode, tap interface is XDP_DROP everything. We vary VHOST_NET_BATCH (1, 16, 32, ...). As Jason put in a previous mail: TX: testpmd(txonly) -> virtio-user -> vhost_net -> XDP_DROP on TAP 1 | 16 | 32 | 64 | 128 | 256 | 512 | 2293304.308| 3396057.769| 3540860.615| 3636056.077| 3332950.846| 3694276.154| 3689820| If we add the batching part of the series, but not the bufapi: 1 | 16 | 32 | 64 | 128 | 256 | 512 | 2286723.857 | 3307191.643| 3400346.571| 3452527.786| 3460766.857| 3431042.5 | 3440722.286| And if we add the bufapi part, i.e., all the series: 1 | 16 | 32 | 64 | 128 | 256 | 512 | 1024 2257970.769| 3151268.385| 3260150.538| 3379383.846| 3424028.846| 3433384.308| 3385635.231| 3406554.538 For easier treatment, all in the same table: 1 | 16 | 32 | 64 | 128 | 256 | 512 | 1024 ------------+-------------+-------------+-------------+-------------+-------------+------------+------------ 2293304.308 | 3396057.769 | 3540860.615 | 3636056.077 | 3332950.846 | 3694276.154 | 3689820 | 2286723.857 | 3307191.643 | 3400346.571 | 3452527.786 | 3460766.857 | 3431042.5 | 3440722.286| 2257970.769 | 3151268.385 | 3260150.538 | 3379383.846 | 3424028.846 | 3433384.308 | 3385635.231| 3406554.538 > > # Rx > > # == The rx tests are done with pktgen injecting packets in tap interface, and testpmd in rxonly forward mode. Again, each column is a different value of VHOST_NET_BATCH, and each row is base, +batching, and +buf_api: > > # pktgen results (pps) (Didn't record extreme cases like >512 bufs batching) 1 | 16 | 32 | 64 | 128 | 256 | 512 -------+--------+--------+--------+--------+--------+-------- 1223275| 1668868| 1728794| 1769261| 1808574| 1837252| 1846436 1456924| 1797901| 1831234| 1868746| 1877508| 1931598| 1936402 1368923| 1719716| 1794373| 1865170| 1884803| 1916021| 1975160 > > # Testpmd pps results 1 | 16 | 32 | 64 | 128 | 256 | 512 | 1024 | 2048 ------------+------------+------------+-----------+-----------+------------+------------+------------+--------- 1222698.143 | 1670604 | 1731040.6 | 1769218 | 1811206 | 1839308.75 | 1848478.75 | 1450140.5 | 1799985.75 | 1834089.75 | 1871290 | 1880005.5 | 1934147.25 | 1939034 | 1370621 | 1721858 | 1796287.75 | 1866618.5 | 1885466.5 | 1918670.75 | 1976173.5 | 1988760.75 | 1978316 The last extreme cases (>512 bufs batched) were recorded just for the bufapi case. Does that make sense now? Thanks!