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

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Message-ID: <20250515120804.32131-1-sarunkod@amd.com>
Date: Thu, 15 May 2025 17:38:04 +0530
From: Sairaj Kodilkar <sarunkod@....com>
To: <seanjc@...gle.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>, Sairaj Kodilkar
	<sarunkod@....com>
Subject: Re: [PATCH 00/67] KVM: iommu: Overhaul device posted IRQs support

Hi Sean,

We ran few tests with following setup

* 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