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 X-Spam-Level: X-Spam-Status: No, score=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7BEFFC7618F for ; Mon, 22 Jul 2019 21:07:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4C41F218F0 for ; Mon, 22 Jul 2019 21:07:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="MBmhPZcX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730501AbfGVVHJ (ORCPT ); Mon, 22 Jul 2019 17:07:09 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:40454 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727845AbfGVVHJ (ORCPT ); Mon, 22 Jul 2019 17:07:09 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; 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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=IFeU/0oltT0V+jaMXcs+mhIGLcUmo4eqxZamdwL0OoU=; b=MBmhPZcX+btbne+QodGupnlko GTn2pfUZoL08+6pgExaN33JzkNmjSCbb3Hn7DxvEQcNIo5vfXtVuQjJNfRD86k+EEpIvX3VoMSOLz Jf7mIe51Wi9VN2yRsipoFsMqyvIKIlfXUo8ciU8YrL7JqI1Hdl6/92h1wIUYYwRlYgEUFfScbEzjJ TGoIH6VRh4KmJLu73yomnzZjXvwZ8W3/YpyaeYB8n1YrWTbUIa523+X9H8ZGEONJfGb3hbHQawCVY zSjT/mDncOGGsmKfFBm5a0yq28vpxUGi/e8KD96M1ys/nlUEwltc0tfbx+rildZ6xNdUOQgNksuPP YaPczcPDQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92 #3 (Red Hat Linux)) id 1hpfWU-0003Hv-Fn; Mon, 22 Jul 2019 21:07:06 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id 47455980D1F; Mon, 22 Jul 2019 23:07:04 +0200 (CEST) Date: Mon, 22 Jul 2019 23:07:04 +0200 From: Peter Zijlstra To: Nadav Amit Cc: Andy Lutomirski , x86@kernel.org, linux-kernel@vger.kernel.org, Dave Hansen , Thomas Gleixner , Ingo Molnar Subject: Re: [RFC 7/7] x86/current: Aggressive caching of current Message-ID: <20190722210704.GL6698@worktop.programming.kicks-ass.net> References: <20190718174110.4635-1-namit@vmware.com> <20190718174110.4635-8-namit@vmware.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190718174110.4635-8-namit@vmware.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 18, 2019 at 10:41:10AM -0700, Nadav Amit wrote: > The current_task is supposed to be constant in each thread and therefore > does not need to be reread. There is already an attempt to cache it > using inline assembly, using this_cpu_read_stable(), which hides the > dependency on the read memory address. Is that what it does?!, I never quite could understand percpu_stable_op().