From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 63EF4231830; Wed, 30 Apr 2025 09:25:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746005128; cv=none; b=l7jgXSiFhJvu+uI9SyGx6toNg89RwAnn2UubIHIg1RjLJg8/HkbHdR0Fskntwr0IzrPXgm5uKKJSem6VAQ4BXPOQt5LcPOAaOj+F7L+IlEYSVxHT71G/u51ROUDLP8p58KjG74+r4R1def+fSbOl6pbo4FX4qfc5WiLB/JtmAek= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746005128; c=relaxed/simple; bh=kM42SKktj2dNOf8NBJOfjLlyuoqhDcyMQafUNOjcJ2A=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=hfy9SRMeOWcgIUq2TUK9PTTUAZKNiJe536QkQFDlkisEpEZVR2l5AJS8vVM/EKVnDOg2FX05synOSBJAPg742NrIKKFk5DuaOiJngpvHfynAroKBzJKft3ZTXysLzNtWKITbRw/MRNDnMCEbUlzxGZVGwrPRurdpphSbWexgUr0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=fNHWhPow; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="fNHWhPow" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=VAVPiUaHOhMsQmm4unIngcxM+UowNmfVEzLvUrtDK6o=; b=fNHWhPowS2BP6NxIKeLPVNmaGP kSeThhyowLUFeenbgk5mMmyhdKRU36jwAMj6OHWVtEvitS5VJCTpcVm2mLuI6kVjYxO5NusXqsDGM aghdecZvFL+dUTUktvkYo4U714PqlLGkKl3IBRcmWGVxJtEOk4c7AEWcvmKGmeu2//lBg7rSKpofk ZuLbtIF9f1KzAfD8t9DDQKpfRFW8vXlfjaTwXb71sqzwvR5Cc0Ljlp3g7VPxaPcp4z8OI31+mrCQ3 wIb+hNsg/fLF67l7N8L/YEV12s/dGJkzpCCymt9bjmE0zG15imy1zMp5B+DR+QWFBI1G4SyncODgi K8cW93wA==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98.1 #2 (Red Hat Linux)) id 1uA3gr-0000000Dl1E-2qXN; Wed, 30 Apr 2025 09:25:18 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id F1155300642; Wed, 30 Apr 2025 11:25:16 +0200 (CEST) Date: Wed, 30 Apr 2025 11:25:16 +0200 From: Peter Zijlstra To: K Prateek Nayak Cc: Jean-Baptiste Roquefere , "mingo@kernel.org" , Juri Lelli , Vincent Guittot , "linux-kernel@vger.kernel.org" , Borislav Petkov , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , "Gautham R. Shenoy" , Swapnil Sapkal , Valentin Schneider , "regressions@lists.linux.dev" , "stable@vger.kernel.org" Subject: Re: IPC drop down on AMD epyc 7702P Message-ID: <20250430092516.GJ4439@noisy.programming.kicks-ass.net> References: <4c0f13ab-c9cd-42c4-84bd-244365b450e2@amd.com> <996ca8cb-3ac8-4f1b-93f1-415f43922d7a@ateme.com> <3daac950-3656-4ec4-bbee-7a3bbad6d631@amd.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3daac950-3656-4ec4-bbee-7a3bbad6d631@amd.com> On Wed, Apr 30, 2025 at 02:43:00PM +0530, K Prateek Nayak wrote: > (+ more scheduler folks) > > tl;dr > > JB has a workload that hates aggressive migration on the 2nd Generation > EPYC platform that has a small LLC domain (4C/8T) and very noticeable > C2C latency. Seems like the kind of chip the cache aware scheduling crud should be good for. Of course, it's still early days on that, so it might not be in good enough shape to help yet. But long term, that should definitely be the goal, rather than finding ways to make relax_domain hacks available again.