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=-2.4 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, 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 13E2DC46472 for ; Mon, 6 Aug 2018 17:50:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B94E621A0D for ; Mon, 6 Aug 2018 17:50:22 +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="dBWisTEN" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B94E621A0D 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-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733119AbeHFUAa (ORCPT ); Mon, 6 Aug 2018 16:00:30 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:46164 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732994AbeHFUAa (ORCPT ); Mon, 6 Aug 2018 16:00:30 -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=QYw4gXF7Klx/au6ypo5XNt5KNSd9SQUIXHTVsEqktBY=; b=dBWisTENPtBA1RFmdvWfXGfx6 Z2E9Acl2VHTltxA2H2xJ9RfwwrO22bePL3h1uL8Dh+3RudSDKtD1bdGKhQdjCD3mKsTnZqj9yaJng bxje/beF30qa+lIx9dI7RlIsHwuocJ7Dgw6MQzsSi5bZXkQJcQSptq4AkpTi0AH3/qiG3ztoqtftw CtMNm5IOUQR+HjBKaIGsuaDN8UFAA/vlzKB6gCxh3invhw52TYYESCTQt/nPaF+OHF00K9JlBy2o/ Ooc4RsNrKz+TCUmA53V0x5p08xPxWWaDvnLe6oXhR0b5TWIX4SWcx9yiL6G92mB+e1WbNkq9ffxIE jY8paXa8A==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fmje3-0004d5-Pi; Mon, 06 Aug 2018 17:50:15 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 549792058A225; Mon, 6 Aug 2018 19:50:13 +0200 (CEST) Date: Mon, 6 Aug 2018 19:50:13 +0200 From: Peter Zijlstra To: Rik van Riel Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, luto@kernel.org, x86@kernel.org, efault@gmx.de, dave.hansen@intel.com Subject: Re: [PATCH 11/11] mm,sched: conditionally skip lazy TLB mm refcounting Message-ID: <20180806175013.GB2476@hirez.programming.kicks-ass.net> References: <20180801100255.4278-1-riel@surriel.com> <20180801100255.4278-12-riel@surriel.com> <20180803155618.GB2494@hirez.programming.kicks-ass.net> <1533314448.28585.101.camel@surriel.com> <20180803172516.GM2458@hirez.programming.kicks-ass.net> <1533317992.28585.103.camel@surriel.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="ev7mvGV+3JQuI2Eo" Content-Disposition: inline In-Reply-To: <1533317992.28585.103.camel@surriel.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --ev7mvGV+3JQuI2Eo Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Aug 03, 2018 at 01:39:52PM -0400, Rik van Riel wrote: > > At the very least the Changelog needs to explain why we cannot do > > away with the swizzle now and how doing the swizzle without the > > refcounting is not completely broken (I think I see, but urgh). >=20 > The changelog for patches 9 & 10 explains, I think. They hint at it :-) > What is missing from my explanation? > How would you like to see it explained? Maybe a few words like: "Since ->active_mm is still used in a few sites, we must keep the current tracking, such that we will not hit a kthread's NULL mm. Note that lazy_tlb_exit_mmap() switches ->active_mm to &init_mm before taking out the lazy mm." That said; I'm not entirely sure we'll actually touch active_mm if we're not a user task. The perf thing for example will only touch active_mm when user_mode(regs). But whatever, this was the only hickup. Acked-by: Peter Zijlstra (Intel) --ev7mvGV+3JQuI2Eo Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEEv3OU3/byMaA0LqWJdkfhpEvA5LoFAltoilUACgkQdkfhpEvA 5LoMbA//QZL9D0E1M8RTfaw4YIR3LURfwijpyAfkFDSHCQZooC2wAM6ULhTLgnDT yVdHaXE8f4fylA6dWWql0mx9KMsUD7AECk4yWYFhxYaJpym3EU0dvRfUOPxCyVb5 Sih9y92LJ9zg/dv1TuoC+A/wVjnCfWI4hBiTCaDUY1oV0PEmUe1vghBOPrLjXHzI xWRb6hDbuVAOSJyoOA87RQUTKGerbQnNRIWKXl64itUpWwYCqTXX71+03Oji1Mad bRyf0WyzP74QA7vKVr8HE2IJifT6XOTVAGyU6SEMTajru7221VO5pyp/PNLYVpCD MGAfa5RVi8pa08NqnREl+iFCyZAxD5eBvPLmJhwY9ESqQygDGjlZT5F7Bv7k0IsO tw+z4/DbZrNnS7zokNYl+9ObvLfhZHiuHoT9nI6qf9+ws029FTRliNV1hYDGGXFm 2pcjD9dRgwZJADT13yXc4wyYjsIx19UIa5YylSEoZCTQgFMWZrtJpMrMc8n4B21z Yg9LCONktrg7b15u6hjvW32Uw7DtehV8myiuRmOArtkW0IP7BRIsog+8drOYGXDU aJKDFQBY61HzDjv/7tEZ7M+kqHbEVJSZKsQGkEy2nJLXLIWlwR0jIGq4rM3Pq1+8 loi6cnUuAJ5aJUvilQl/PE1203Zacbkoo9DsbgMqM3Kh+vhpglE= =Y+R9 -----END PGP SIGNATURE----- --ev7mvGV+3JQuI2Eo--