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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 77252C2BA19 for ; Tue, 21 Apr 2020 08:31:09 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 499172084D for ; Tue, 21 Apr 2020 08:31:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="qiwnFLzr" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 499172084D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=IcXLkQalUDav6k/V0y4c7z4902rvNjpGA2pYVObxnis=; b=qiwnFLzrQkfwHD xjXb6oqLMmID2fnBm6Y4Ygllh4lY+xrix+hKXPdqRa0NV9KRLwRBaVtDnxCeWPx+yMDQoS9jmNdAH UPTBMII+Pq1q6H4gs9Fs1R1w0k2xBvvHw4h2QbR5w5aHEmkMDpSD7hankEmkyKt3l/uCD9R+vB/Ze keliuYfdDhK7UBStqcsUcFgbJKl9gr3iFAHbAS6F1u13xUQKQ0DJOpYKYXJCZqisS4S4uTtTZajjX hCvLoeHp7c3wIHjeMQpHWoczI6ljhTofTzlG7c+PK1lE7Np1dzag24f8HGnG1ihM4SsYdd48d1vFH L+JnKqrr2bVWm/3L23mA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jQoJ8-0000cR-RQ; Tue, 21 Apr 2020 08:31:06 +0000 Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jQoIr-0000KX-6O; Tue, 21 Apr 2020 08:30:51 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 22C7A306108; Tue, 21 Apr 2020 10:30:43 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id E21502B9EA39A; Tue, 21 Apr 2020 10:30:43 +0200 (CEST) Date: Tue, 21 Apr 2020 10:30:43 +0200 From: Peter Zijlstra To: Steven Rostedt Subject: Re: [PATCH v1 6/6] arm64: tlb: Set the TTL field in flush_tlb_range Message-ID: <20200421083043.GP20730@hirez.programming.kicks-ass.net> References: <20200403090048.938-1-yezhenyu2@huawei.com> <20200403090048.938-7-yezhenyu2@huawei.com> <20200420121055.GF20696@hirez.programming.kicks-ass.net> <20200420200616.44c7c7ea@oasis.local.home> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200420200616.44c7c7ea@oasis.local.home> X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, catalin.marinas@arm.com, linux-mm@kvack.org, guohanjun@huawei.com, will@kernel.org, linux-arch@vger.kernel.org, yuzhao@google.com, maz@kernel.org, suzuki.poulose@arm.com, steven.price@arm.com, arm@kernel.org, Dave.Martin@arm.com, arnd@arndb.de, Zhenyu Ye , npiggin@gmail.com, zhangshaokun@hisilicon.com, broonie@kernel.org, xiexiangyou@huawei.com, prime.zeng@hisilicon.com, kuhn.chenqun@huawei.com, tglx@linutronix.de, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, aneesh.kumar@linux.ibm.com, akpm@linux-foundation.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Apr 20, 2020 at 08:06:16PM -0400, Steven Rostedt wrote: > Peter Zijlstra wrote: > > On Fri, Apr 03, 2020 at 05:00:48PM +0800, Zhenyu Ye wrote: > > > +static inline int tlb_get_level(struct mmu_gather *tlb) > > > +{ > > > + int sum = tlb->cleared_ptes + tlb->cleared_pmds + > > > + tlb->cleared_puds + tlb->cleared_p4ds; > > > + > > > + if (sum != 1) > > > + return 0; > > > + else if (tlb->cleared_ptes) > > > + return 3; > > > + else if (tlb->cleared_pmds) > > > + return 2; > > > + else if (tlb->cleared_puds) > > > + return 1; > > > + > > > + return 0; > > > +} > > > > That's some mighty wonky code. Please look at the generated asm. > > Without even looking at the generated asm, if a condition returns, > there's no reason to add an else for that condition. Not really the point; he wants to guarantee he only returns >0 when there's a single bit set. But the thing is, cleared_* is a bitfield, and I'm afraid that the above will result in some terrible code-gen. Maybe something like: if (tlb->cleared_ptes && !(tlb->cleared_pmds || tlb->cleared_puds || tlb->cleared_p4ds)) return 3; if (tlb->cleared_pmds && !(tlb->cleared_ptes || tlb->cleared_puds || tlb->cleared_p4ds)) return 2; if (tlb->cleared_puds && !(tlb->cleared_ptes || tlb->cleared_pmds || tlb->cleared_p4ds)) return 1; return 0; Which I admit is far too much typing, but I suspect it generates far saner code (just a few masks and branches). But maybe the compiler surprises us, what do I konw. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel