From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 01D0634D4CE for ; Wed, 14 Oct 2026 09:03:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791968597; cv=none; b=gSpYRVTqUemx2ubh9b+vIj3k1epB4RKtjCiwouR151W0Z3NkedrdED9dGHUppOPqXFPhcEPvOsRPb25gdPWiFXDJ9SJKdNfxEfunJ5CXC51DOUZRJIcyYvw9XvQd3NMTsUkaurJsB+kDioIA+uxkgli4u4W+hvrG9YHOH2tdoxY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791968597; c=relaxed/simple; bh=7A05GsuFKMCSCusEHwAE+GYyrPrUSYy7spZfdDk0d+k=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=nL6ZBCsZefNUqt+SZrGh5wH4jYl33XD+fjrO0gondX8WMjZhtk07Hu37v6pKeSkqqmlgROc7rXJ2WOEMSL1GkXOt/yKebKx7qVPBlcDAGhPAdCbrmqc8UYV3uuXPB6zo/pinuNuv0i6duQpuYS82mCsoDXgjzyKmdqGpDnwRvPU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=YoKyykGB; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="YoKyykGB" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A34661596; Wed, 14 Oct 2026 02:03:04 -0700 (PDT) Received: from arm.com (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 334523F7B4; Wed, 14 Oct 2026 02:03:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1791968587; bh=7A05GsuFKMCSCusEHwAE+GYyrPrUSYy7spZfdDk0d+k=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=YoKyykGBv0d5ue1IA9pDqAIBz0IsC4ds1IPAVcDI3VyYRFIpLsbgh+PjOfqESJYLM nKkMwtRvL8O0B3NL+W7trm/B/1/A1l/+YsTkw6Y3cm3AJ6d5wvTe7xoa967irdGd/t ou+P9TNgOMpuhAmmkHefuL9+QewRyRRDClluU2po= Date: Wed, 14 Oct 2026 10:03:02 +0100 From: Catalin Marinas To: Linus Walleij Cc: Muhammad Usama Anjum , Leonardo Bras , Will Deacon , Marc Zyngier , Oliver Upton , Joey Gouly , Suzuki K Poulose , Zenghui Yu , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev Subject: Re: [PATCH v2] arm64: clear_page[s] using memset Message-ID: References: <20260916-aarch64-clear-pages-c-v2-1-0393769f7912@kernel.org> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Tue, Oct 13, 2026 at 06:28:54PM +0200, Linus Walleij wrote: > On Tue, Oct 13, 2026 at 3:04 PM Catalin Marinas wrote: > > > Trying to make sense of the above. So based on -next of 22nd of > > September, the table means: > > > > vanilla - next/master on that day (current clear_page()) > > patch - memset()-based clear_page() patch (Linus's patch) > > stnp - vanilla clear_page() without DC ZVA > > patch_stp - memset()-based clear_page() patch without DC ZVA > > > > I assume the vanilla vs patch columns are just noise. Well, there's a > > -1.17% regression (not flagged) on Ampere but what's the standard > > deviation for this column? Similarly for the -1.15% on the AWS patch_stp > > test (vs stnp in the same test, it's no worse). > > > > Vanilla vs stnp shows a regression on Ampere, however that's expected as > > we no longer do the DC ZVA. Interestingly, the patch_stp result doesn't have > > this regression, so I reckon DC ZVA behaves mostly in line with STP on > > this hardware. > > > > Basically I was looking for the stnp vs patch_stp results. If I read it > > correctly, there's no significant change going from non-temporal to > > temporal stores (and a small improvement for Ampere). Assuming future > > FEAT_MOPS will have similar behaviour, moving clear_page() to memset() > > shouldn't cause any regressions. Before FEAT_MOPS, we'll use DC ZVA here > > anyway. > > That almost sounds like an Acked-by if Usama can confirm your > assumptions above! It's queued but we can revert it if it shows real regression. -- Catalin