linux-kernel - Re: [PATCH 00/67] KVM: iommu: Overhaul device posted IRQs support

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Message-ID: <aCZlNYlhSKXRFvnc@google.com>
Date: Thu, 15 May 2025 15:05:41 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sairaj Kodilkar <sarunkod@....com>
Cc: baolu.lu@...ux.intel.com, dmatlack@...gle.com, dwmw2@...radead.org, 
	iommu@...ts.linux.dev, joao.m.martins@...cle.com, joro@...tes.org, 
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, mlevitsk@...hat.com, 
	pbonzini@...hat.com, vasant.hegde@....com, suravee.suthikulpanit@....com, 
	naveen.rao@....com
Subject: Re: [PATCH 00/67] KVM: iommu: Overhaul device posted IRQs support

On Thu, May 15, 2025, Sairaj Kodilkar wrote:
> Hi Sean,
> 
> We ran few tests with following setup

A few!!?!?  This is awesome!  Thank you, I greatly appreciate the testing!

> * Turin system with 2P, 192 cores each (SMT enabled, Total 768)
> * 4 NVMEs of size 1.7 attached to a single IOMMU
> * Total RAM 247 GiB
> * Qemu version : 9.1.93
> * Guest kernel : 6.14-rc7
> * FIO random reads with 4K blocksize and libai
> 
> With above setup we measured the Guest nvme interrupts, IOPS, GALOG interrupts
> and GALOG entries for 60 seconds with and without your changes.
> 
> Here are the results,
> 
>                           VCPUS = 32, Jobs per NVME = 8
> ==============================================================================================
>                              w/o Sean's patches           w/ Sean's patches     Percent change
> ----------------------------------------------------------------------------------------------
> Guest Nvme interrupts               123,922,860                 124,559,110              0.51%
> IOPS (in kilo)                            4,795                       4,796              0.04%
> GALOG Interrupts                         40,245                         164            -99.59%
> GALOG entries                            42,040                         169            -99.60%
> ----------------------------------------------------------------------------------------------
> 
> 
>                 VCPUS = 64, Jobs per NVME = 16
> ==============================================================================================
>                              w/o Sean's patches           w/ Sean's patches     Percent change
> ----------------------------------------------------------------------------------------------
> Guest Nvme interrupts               99,483,339                   99,800,056             0.32% 
> IOPS (in kilo)                           4,791                        4,798             0.15% 
> GALOG Interrupts                        47,599                       11,634           -75.56% 
> GALOG entries                           48,899                       11,923           -75.62%
> ----------------------------------------------------------------------------------------------
> 
> 
>                 VCPUS = 192, Jobs per NVME = 48
> ==============================================================================================
>                              w/o Sean's patches          w/ Sean's patches      Percent change
> ----------------------------------------------------------------------------------------------
> Guest Nvme interrupts               76,750,310                  78,066,512               1.71%
> IOPS (in kilo)                           4,751                       4,749              -0.04%
> GALOG Interrupts                        56,621                      54,732              -3.34%
> GALOG entries                           59,579                      56,215              -5.65%
> ----------------------------------------------------------------------------------------------
>  
> 
> The results show that patches have significant impact on the number of posted
> interrupts at lower vCPU count (32 and 64) while providing similar IOPS and
> Guest NVME interrupt rate (i.e. patches do not regress).
> 
> Along with the performance evaluation, we did sanity tests such with AVIC,
> x2AVIC and kernel selftest.  All tests look good.
> 
> For AVIC related patches:
> Tested-by: Sairaj Kodilkar <sarunkod@....com>
> 
> Regards
> Sairaj Kodilkar
>