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Date: Mon, 3 Nov 2025 15:03:53 -0800
From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Josh Poimboeuf <jpoimboe@kernel.org>,
	David Kaplan <david.kaplan@amd.com>,
	Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
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	Asit Mallick <asit.k.mallick@intel.com>,
	Tao Zhang <tao1.zhang@intel.com>
Subject: Re: [PATCH v3 0/3] VMSCAPE optimization for BHI variant
Message-ID: <20251103230353.ifsayclvtw7bzyga@desk>
References: <20251027-vmscape-bhb-v3-0-5793c2534e93@linux.intel.com>
 <f07e3144-edcd-4b5c-8b4a-fb6bdd90943b@intel.com>
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In-Reply-To: <f07e3144-edcd-4b5c-8b4a-fb6bdd90943b@intel.com>

On Mon, Nov 03, 2025 at 12:07:30PM -0800, Dave Hansen wrote:
> On 10/27/25 16:43, Pawan Gupta wrote:
> > | iPerf user-net | IBPB    | BHB Clear |
> > |----------------|---------|-----------|
> > | UDP 1-vCPU_p1  | -12.5%  |   1.3%    |
> ...
> 
> Could you clarify what "1.3%" means? Is that relative to the baseline,
> or relative to the IBPB number?

This is relative to the baseline, sorry I didn't mention that explicitly.

> If it's relative to the baseline, then this data either looks wrong or
> noisy since there are a lot of places where adding the BHB Clear loop
> makes things faster.

I will double check, but I am fairly positive that this wasn't noisy.
Surprisingly, there were a few other cases where the BHB-clearing was
performing better than the baseline.