From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-180.mta0.migadu.com (out-180.mta0.migadu.com [91.218.175.180]) (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 C5AB8145B24 for ; Thu, 8 Aug 2024 17:55:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723139758; cv=none; b=XgnNq0AHX23XT1vJfY0JlRmrJNbGTuztfCB7Lo38Bmp/WG3pIhvmD58DoJ1jE1YaRrm4UMFlUMd5CRpdqlnb1pnXyvieQ+PBgZEHf7wT3BGbtGJhCsFGmHQOEVy5E2d60CY7Qd3zuUD/n7cI3eFVsoQipnoq6u3YRBRy/xmuef4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723139758; c=relaxed/simple; bh=8cBJ/OUasyDlaDm+uV6M4jjd+cY/+LKS0yu/8qagYyg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=WM0Io9M/OvAY9b3N0+5h2uhN4SSnwo1q41ISZ/sjsSEsgLSoNDjvXgf8K5AFpmxpiE+Af1lUbbwhQjv6v6cG3WgL5K8mPo5gf41NagXbWrIGhI9C+D+BsLSWriYLccuNAeJ+I1jwwOBgVWZfv0p7ajkAjarnUTb1rWP9dxmNolM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=lHymnHH+; arc=none smtp.client-ip=91.218.175.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="lHymnHH+" Date: Thu, 8 Aug 2024 17:55:49 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1723139754; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=DHyamLELFxFvqyuXfn2/colLtUh6a7qi/U4t10FKUEY=; b=lHymnHH+dqyrt+owmksdWDKCRhPs0AE+y6sFwQXdVtonO8WOAhxZzK5l2z3DN5R5n7UC37 k/ISQkrwhrvMooAe4gpq4IR3bmVLYto3Klkn80e7zjgbAdbsHSa9dY7mA4NQAnLYt8VmFd l1eSM9M6ectq/stI5676oH8yYrIhk8s= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Oliver Upton To: Colton Lewis Cc: kvm@vger.kernel.org, Marc Zyngier , Ricardo Koller , James Morse , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] KVM: arm64: Move data barrier to end of split walk Message-ID: References: <20240808174243.2836363-1-coltonlewis@google.com> Precedence: bulk X-Mailing-List: linux-kernel@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: <20240808174243.2836363-1-coltonlewis@google.com> X-Migadu-Flow: FLOW_OUT Hi Colton, On Thu, Aug 08, 2024 at 05:42:43PM +0000, Colton Lewis wrote: > This DSB guarantees page table updates have been made visible to the > hardware table walker. Moving the DSB from stage2_split_walker() to > after the walk is finished in kvm_pgtable_stage2_split() results in a > roughly 70% reduction in Clear Dirty Log Time in > dirty_log_perf_test (modified to use eager page splitting) when using > huge pages. This gain holds steady through a range of vcpus > used (tested 1-64) and memory used (tested 1-64GB). Would you have time to put together a patch for the dirty_log_perf_test changes you've made? This would be quite valuable for testing future improvements to eager page splitting. > This is safe to do because nothing else is using the page tables while > they are still being mapped and this is how other page table walkers > already function. None of them have a data barrier in the walker > itself because relative ordering of table PTEs to table contents comes > from the release semantics of stage2_make_pte(). > > Signed-off-by: Colton Lewis The diff itself looks good to me, so: Acked-by: Oliver Upton -- Thanks, Oliver