Monday, April 20, 2020 10:13 AM, Maxime Coquelin: > Subject: Re: [PATCH 1/4] vhost: inroduce operation to get vDPA queue stats > > Hi Shahaf, > > On 4/19/20 8:18 AM, Shahaf Shuler wrote: > > Thursday, April 16, 2020 4:20 PM, Maxime Coquelin: > >> Subject: Re: [PATCH 1/4] vhost: inroduce operation to get vDPA queue > >> stats > >> > >> Hi Matan, > >> > >> On 4/16/20 11:06 AM, Matan Azrad wrote: > >>> Hi Maxime > >>> > >>> Can you point on specific vendor specific counter I suggested? > >> > >> No, I can't, but I think we can expect that other vendors may have > >> other counters they would be interested to dump. > >> > >> Maybe Intel has some counters in the IFC that they could dump. > >> Xiao, any thoughts? > >> > >>> I think all of them come directly from virtio protocols. > >> > >> exceed_max_chain, for example. Doesn't the spec specify that a > >> descriptors chain can be as long as the size of the virtqueue? > >> > >> Here it seems to indicate the device could support less. > > > > Spec allows device to limit the max supported chain (see [1]). > > Ha ok, I missed that. Please note that this is only allowed for packed ring, > it is > not in the split ring part.
On my version of spec (csprd01) it is also for split, however it was removed on the latest version not sure why. > > >> > >> Also, as the spec evolves, we may have new counters that comes up, so > >> better to have something flexible from the start IMHO to avoid ABI > >> breakages. > > > > I think there are better ways to address that, e.g.: > > 1. have some reserved fields for future 2. have the option to point to > > next item, and by that link chain of stat structures > > > >> > >> Maybe we can have some common xstats names for the Virtio related > >> counters define in vdpa lib, and then the vendors can specify more > >> vendor- specific counters if they wish? > > > > xstats are good, and we should have it to expose the vendor specific > counters. The basic counters though, should be simple and vendor agnostic > so that any SW/scripting layer on top of the DPDK can easily use and expose > it. > > Hence I think it will be good to have the basic counters with well-defined > stats structure as part of the vdpa stats API. Is the exceed_max_chain is the > only counter you find odd or there are more? > > Problem is that not all the vDPA NIC will implement these counters, so with > only proposed implementation, the user cannot know whether counter > value is 0 or counter is just not implemented. For example, the Virtio > specification does not specify counters, so a full Virtio HW offload device > won't have them. Yeah, full virtio emulated device is a good example. I think it is odd virtio doesn’t provide any statistics, e.g. how would the Netdev on top of the virtio device report anything? How will ppl debug? I think sooner or later we will need a way to expose stats. > > So I think the xstat is the right thing to do, with standardized names for the > standard counters. Yeah tend to agree on this one due to the lack of spec statistics. > > Regards, > Maxime > >> > >> Thanks, > >> Maxime > > > > [1] > > https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgith > > ub.com%2Foasis-tcs%2Fvirtio-spec%2Fblob%2Fmaster%2Fpacked- > ring.tex%23L > > > 498&data=02%7C01%7Cshahafs%40mellanox.com%7C2fbf00c6e115488f > 483e08 > > > d7e4fa4940%7Ca652971c7d2e4d9ba6a4d149256f461b%7C0%7C0%7C6372296 > 3594175 > > > 9512&sdata=m2rPPMM%2Fen9Vkbp%2Fg5xz0MSTWYURh7woI7w5%2B > b2Zjy8%3D&am > > p;reserved=0 > >
