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=-5.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 022DBC3A5A3 for ; Tue, 27 Aug 2019 21:50:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C98992064A for ; Tue, 27 Aug 2019 21:50:53 +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="LfNIE058" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726421AbfH0Vuw (ORCPT ); Tue, 27 Aug 2019 17:50:52 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:35942 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725804AbfH0Vuw (ORCPT ); Tue, 27 Aug 2019 17:50:52 -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=FB8pN+BfPxkb7VhVcHVNo4pDuBs87uFREFm8kjgxbXI=; b=LfNIE0589Ir9nLcNlwkc4H5Gr q8+xmVwFYXlyGZIMD1twy/HYuEsVWkM29dacB5CxEQaq1LE+E7pmg0QDl8iIRE0VHaedB4giOhHJo G+1tmfRtbau8m8fboQbiuo0Z8g0G7blndf4vbOs3WOTS4jVAjTsk2JkiFV2N5NndH947kxdWc5OhT v2SvywIk5gES4IjtsmzvZ8FLv8b14R3I9Tv2QzchtvciiFiwBtf4rvuBzTHa4y9KaF6iJsPehkE3c prqkLJ7NwyJt6aJNR1/Jt1twuPjSbhBN6XH+Tlkv8o0e8yLxawYLmTeSWnGnUwrRErTNARwt6d91a 9XSyawtYg==; 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 (Red Hat Linux)) id 1i2jMN-00033M-19; Tue, 27 Aug 2019 21:50:39 +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 6036330768B; Tue, 27 Aug 2019 23:50:02 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id DA5CF203CEC05; Tue, 27 Aug 2019 23:50:35 +0200 (CEST) Date: Tue, 27 Aug 2019 23:50:35 +0200 From: Peter Zijlstra To: Matthew Garrett Cc: Vineeth Remanan Pillai , Nishanth Aravamudan , Julien Desfossez , Tim Chen , mingo@kernel.org, tglx@linutronix.de, pjt@google.com, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, subhra.mazumdar@oracle.com, fweisbec@gmail.com, keescook@chromium.org, kerrnel@google.com, Phil Auld , Aaron Lu , Aubrey Li , Valentin Schneider , Mel Gorman , Pawan Gupta , Paolo Bonzini Subject: Re: [RFC PATCH v3 00/16] Core scheduling v3 Message-ID: <20190827215035.GH2332@hirez.programming.kicks-ass.net> References: <20190827211417.snpwgnhsu5t6u52y@srcf.ucam.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190827211417.snpwgnhsu5t6u52y@srcf.ucam.org> 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 Tue, Aug 27, 2019 at 10:14:17PM +0100, Matthew Garrett wrote: > Apple have provided a sysctl that allows applications to indicate that > specific threads should make use of core isolation while allowing > the rest of the system to make use of SMT, and browsers (Safari, Firefox > and Chrome, at least) are now making use of this. Trying to do something > similar using cgroups seems a bit awkward. Would something like this be > reasonable? Sure; like I wrote earlier; I only did the cgroup thing because I was lazy and it was the easiest interface to hack on in a hurry. The rest of the ABI nonsense can 'trivially' be done later; if when we decide to actually do this. And given MDS, I'm still not entirely convinced it all makes sense. If it were just L1TF, then yes, but now... > Having spoken to the Chrome team, I believe that the > semantics we want are: > > 1) A thread to be able to indicate that it should not run on the same > core as anything not in posession of the same cookie > 2) Descendents of that thread to (by default) have the same cookie > 3) No other thread be able to obtain the same cookie > 4) Threads not be able to rejoin the global group (ie, threads can > segregate themselves from their parent and peers, but can never rejoin > that group once segregated) > > but don't know if that's what everyone else would want. > > diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h > index 094bb03b9cc2..5d411246d4d5 100644 > --- a/include/uapi/linux/prctl.h > +++ b/include/uapi/linux/prctl.h > @@ -229,4 +229,5 @@ struct prctl_mm_map { > # define PR_PAC_APDBKEY (1UL << 3) > # define PR_PAC_APGAKEY (1UL << 4) > > +#define PR_CORE_ISOLATE 55 > #endif /* _LINUX_PRCTL_H */ > diff --git a/kernel/sys.c b/kernel/sys.c > index 12df0e5434b8..a054cfcca511 100644 > --- a/kernel/sys.c > +++ b/kernel/sys.c > @@ -2486,6 +2486,13 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, > return -EINVAL; > error = PAC_RESET_KEYS(me, arg2); > break; > + case PR_CORE_ISOLATE: > +#ifdef CONFIG_SCHED_CORE > + current->core_cookie = (unsigned long)current; This needs to then also force a reschedule of current. And there's the little issue of what happens if 'current' dies while its children live on, and current gets re-used for a new process and does this again. > +#else > + result = -EINVAL; > +#endif > + break; > default: > error = -EINVAL; > break; > > > -- > Matthew Garrett | mjg59@srcf.ucam.org