From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH RFC v8 02/11] vhost: use batched get_vq_desc version Date: Tue, 21 Jul 2020 10:55:16 +0800 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; format=flowed Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: =?UTF-8?Q?Eugenio_P=c3=a9rez?= , "Michael S. Tsirkin" Cc: 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 2020/7/20 下午7:16, Eugenio Pérez wrote: > 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! I wonder why we saw huge difference between TX and RX pps. Have you used samples/pktgen/XXX for doing the test? Maybe you can paste the perf record result for the pktgen thread + vhost thread. Thanks >