linux-kernel - Re: performance anomaly in rep movsq/movsb as seen on Sapphire Rapids executing sync

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Message-ID: <e600cb9f-e6d4-461a-b7c5-de60162cd6fc@intel.com>
Date: Wed, 3 Dec 2025 13:35:52 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: david laight <david.laight@...box.com>, Mateusz Guzik <mjguzik@...il.com>
Cc: x86@...nel.org, glx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com, hpa@...or.com, linux-kernel@...r.kernel.org,
 torvalds@...ux-foundation.org, olichtne@...hat.com, atomasov@...hat.com,
 aokuliar@...hat.com
Subject: Re: performance anomaly in rep movsq/movsb as seen on Sapphire Rapids
 executing sync_regs()

On 11/27/25 01:58, david laight wrote:
> I wonder if Sapphire Rapids has some similar perversion?
> Or, is that one of the big/little cpu where most of the cpu are
> actually atom ones - which may not have either ERMS or FSRM ?

No, if it's really Sapphire Rapids, then the CPUs are homogeneous.