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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 8BC89C43387 for ; Thu, 17 Jan 2019 09:02:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4C5AB20855 for ; Thu, 17 Jan 2019 09:02:52 +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="YTu6rxWc" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727826AbfAQJCu (ORCPT ); Thu, 17 Jan 2019 04:02:50 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:56034 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725991AbfAQJCu (ORCPT ); Thu, 17 Jan 2019 04:02:50 -0500 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=XAoos3UGtKwWZX9H/mGqjf00n0NGLotPlsblsRqXSb4=; b=YTu6rxWc3FQhzcXk3EPBU7HLR OyTcM1f9sS+6kF4/dVoOiKp7CInaF4VTp0EiSmTfXRJQQ7/W/5jP8KonkowGVKrIqaMfiWeRU9je5 JdkFycpKIs5gVzdRP72xc0breLM7wMeHKOyDQwsHuHIKniHsaArS6313YXeXrat/4HSzD6OBn+TdG lK3d9GrluWcorLd5oSjaRJ+uhRR7MzmSPenrDm1V48o/T8q3VVbkGRvr0/INmLgsCX6p0kCXPAZ3p v9S1sckbTwakh55iMk1TPS/zJOgjwyk+EItRLxvtawaefglh4KMJYL0C1CwW/bPPIcnbWcd2xcXB7 3oo01m5Lw==; Received: from hch by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gk3ZU-0006xa-40; Thu, 17 Jan 2019 09:02:44 +0000 Date: Thu, 17 Jan 2019 01:02:43 -0800 From: Christoph Hellwig To: "Andrew F. Davis" Cc: Laura Abbott , Liam Mark , Sumit Semwal , Greg Kroah-Hartman , Arve =?iso-8859-1?B?SGr4bm5lduVn?= , devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org, dri-devel Subject: Re: [PATCH 13/14] staging: android: ion: Do not sync CPU cache on map/unmap Message-ID: <20190117090243.GA21651@infradead.org> References: <20190111180523.27862-1-afd@ti.com> <20190111180523.27862-14-afd@ti.com> <79eb70f6-00b0-2939-5ec9-65e196ab4987@ti.com> <99ca0b08-02bd-64fd-d43c-c330f0d11639@ti.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <99ca0b08-02bd-64fd-d43c-c330f0d11639@ti.com> User-Agent: Mutt/1.9.2 (2017-12-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 16, 2019 at 10:17:23AM -0600, Andrew F. Davis wrote: > I wouldn't go as far as to remove them just yet.. Liam seems pretty > adamant that they have valid uses. I'm just not sure performance is one > of them, maybe in the case of software locks between devices or > something where there needs to be a lot of back and forth interleaved > access on small amounts of data? We shouldn't add unused features to start with. If mainline users for them appear we can always add them back once we've reviewed the uses cases and agree that they are sane and have no better solution.