From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4E283C2D0D1 for ; Mon, 24 Jun 2024 17:57:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=6V/lqEaFydKDuF/MgqvOeK9lGE6NarolpWLYw4sb3eU=; b=3uqM9+1AQfD58nfSPGyVLwvCUS KSWmVK++3uf9MwmNeLGKBqw7HWpa0ZfKzEqAH1931EK46YszPVTN70KumLXdZU1dOKFjW6v8R62tt QnCn6GQCaGwWDVRDF3eoxD2UsiGw9BiNLnx1PIFbrJE+EZ9RH6yQelXD9R3Mqy1u0EzE88IvAGBWk YOqvW/Uoxz5IKki3f6UZ6eU6nexoA0Qat9mQKBwBQp7DCJ96CCney6BWAYnPt+kOd+0Ooxnb0ZA7Q idAKA6mCpRwOlH+zPBlIsOE8pRkBaXzvovW/7NdbhfYzrMonuO1kF6NFidUtsJyR8yOUXKfjSSUie WXYG/fOA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sLnvt-00000000C7R-2dU1; Mon, 24 Jun 2024 17:56:49 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sLnvh-00000000C43-4AfP for linux-arm-kernel@lists.infradead.org; Mon, 24 Jun 2024 17:56:39 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id BB78360FA4 for ; Mon, 24 Jun 2024 17:56:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8DE0BC2BBFC; Mon, 24 Jun 2024 17:56:35 +0000 (UTC) Date: Mon, 24 Jun 2024 18:56:33 +0100 From: Catalin Marinas To: Jisheng Zhang Cc: Will Deacon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] arm64/lib: copy_page: s/stnp/stp Message-ID: References: <20240613001812.2141-1-jszhang@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240613001812.2141-1-jszhang@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240624_105638_115235_055B842B X-CRM114-Status: GOOD ( 11.80 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Jun 13, 2024 at 08:18:12AM +0800, Jisheng Zhang wrote: > stnp performs non-temporal store, give a hints to the memory system > that caching is not useful for this data. But the scenario where > copy_page() used may not have this implication, although I must admit > there's such case where stnp helps performance(good). In this good > case, we can rely on the HW write streaming mechanism in some > implementations such as cortex-a55 to detect the case and take actions. > > testing with https://github.com/apinski-cavium/copy_page_benchmark > this patch can reduce the time by about 3% on cortex-a55 platforms. What about other CPUs? I'm also not convinced by such microbenchmarks. It looks like it always copies to the same page, the stp may even benefit from some caching of the data which we wouldn't need in a real scenario. So, I'm not merging this unless it's backed by some solid data across several CPU implementations. -- Catalin