Hello Konrad, Actually I didn’t get that, do you mean you are taking 1G and <=4G cases out of the patch and only going to apply the >4G case as part of the patch ?
Thanks, Ashish > On Nov 17, 2020, at 11:38 AM, Kalra, Ashish <[email protected]> wrote: > > Hello Konrad, > >> On Tue, Nov 17, 2020 at 12:00:03PM -0500, Konrad Rzeszutek Wilk wrote: >> .snip.. >>>>>> Lets break this down: >>>>>> >>>>>> How does the performance improve for one single device if you increase >>>>>> the SWIOTLB? >>>>>> Is there a specific device/driver that you can talk about that improve >>>>>> with this patch? >>>>>> >>>>>> >>>>> >>>>> Yes, these are mainly for multi-queue devices such as NICs or even >>>>> multi-queue virtio. >>>>> >>>>> This basically improves performance with concurrent DMA, hence, >>>>> basically multi-queue devices. >>>> >>>> OK, and for _1GB_ guest - what are the "internal teams/external customers" >>>> amount >>>> of CPUs they use? Please lets use real use-cases. >>> >>>>> I am sure you will understand we cannot share any external customer >>>>> data as all that customer information is proprietary. >>>>> >>>>> In similar situation if you have to share Oracle data, you will >>>>> surely have the same concerns and i don't think you will be able >>>>> to share any such information externally, i.e., outside Oracle. >>>>> >>>> I am asking for a simple query - what amount of CPUs does a 1GB >>>> guest have? The reason for this should be fairly obvious - if >>>> it is a 1vCPU, then there is no multi-queue and the existing >>>> SWIOTLB pool size as it is OK. >>>> >>>> If however there are say 2 and multiqueue is enabled, that >>>> gives me an idea of how many you use and I can find out what >>>> the maximum pool size usage of virtio there is with that configuration. >>> >>> Again we cannot share any customer data. >>> >>> Also i don't think there can be a definitive answer to how many vCPUs a >>> 1GB guest will have, it will depend on what kind of configuration we are >>> testing. >>> >>> For example, i usually setup 4-16 vCPUs for as low as 512M configured >>> gueest memory. >> >> Sure, but you are not the normal user. >> >> That is I don't like that for 1GB guests your patch ends up doubling the >> SWIOTLB memory pool. That seems to me we are trying to solve a problem >> that normal users will not hit. That is why I want 'here is the customer >> bug'. >> >> Here is what I am going to do - I will take out the 1GB and 4GB case out of >> your patch and call it a day. If there are customers who start reporting >> issues >> we can revist that. Nothing wrong with 'Reported-by' XZY (we often ask the >> customer if he or she would like to be recognized on upstream bugs). >> > > Ok. > >> And in the meantime I am going to look about adding .. >>> >>> I have been also testing with 16 vCPUs configuration for 512M-1G guest >>> memory with Mellanox SRIOV NICs, and this will be a multi-queue NIC >>> device environment. >> >> .. late SWIOTLB expansion to stich the DMA pools together as both >> Mellanox and VirtIO are not 32-bit DMA bound. >> >>> >>> So we might be having less configured guest memory, but we still might >>> be using that configuration with I/O intensive workloads. >>> > > I am going to submit v4 of my current patch-set which uses max() instead > of clamp() and also replaces constants defined in this patch with the > pre-defined ones in sizes.h > > Thanks, > Ashish _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
