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>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Asit Mallick <asit.k.mallick@intel.com>,
Tao Zhang <tao1.zhang@intel.com>
Subject: Re: [PATCH v3 0/3] VMSCAPE optimization for BHI variant
Date: Mon, 3 Nov 2025 15:03:53 -0800 [thread overview]
Message-ID: <20251103230353.ifsayclvtw7bzyga@desk> (raw)
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.
prev parent reply other threads:[~2025-11-03 23:03 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-27 23:43 [PATCH v3 0/3] VMSCAPE optimization for BHI variant Pawan Gupta
2025-10-27 23:43 ` [PATCH v3 1/3] x86/bhi: Add BHB clearing for CPUs with larger branch history Pawan Gupta
2025-11-03 20:04 ` Dave Hansen
2025-11-03 22:45 ` Pawan Gupta
2025-10-27 23:43 ` [PATCH v3 2/3] x86/vmscape: Replace IBPB with branch history clear on exit to userspace Pawan Gupta
2025-10-29 22:47 ` Sean Christopherson
2025-10-30 0:08 ` Pawan Gupta
2025-11-03 20:31 ` Dave Hansen
2025-11-06 23:40 ` Pawan Gupta
2025-11-19 10:33 ` Nikolay Borisov
2025-11-19 18:26 ` Pawan Gupta
2025-10-27 23:43 ` [PATCH v3 3/3] x86/vmscape: Remove LFENCE from BHB clearing long loop Pawan Gupta
2025-11-03 20:45 ` Dave Hansen
2025-11-04 22:01 ` Pawan Gupta
2025-11-04 22:35 ` Dave Hansen
2025-11-04 23:36 ` Pawan Gupta
2025-11-03 20:07 ` [PATCH v3 0/3] VMSCAPE optimization for BHI variant Dave Hansen
2025-11-03 23:03 ` Pawan Gupta [this message]
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