Received: by 2002:a05:6a10:af89:0:0:0:0 with SMTP id iu9csp690093pxb; Fri, 14 Jan 2022 14:08:59 -0800 (PST) X-Google-Smtp-Source: ABdhPJzAm5XbIHYC7HW5RzW9c7BYLR+NF5DwKrSUojprB0R02fE6I57UnJKSb4eEF2eUayqiJOgg X-Received: by 2002:aa7:cd06:: with SMTP id b6mr10826316edw.189.1642198139463; Fri, 14 Jan 2022 14:08:59 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1642198139; cv=none; d=google.com; s=arc-20160816; b=nkIm40UqPuXImTUq4fBALPbGzB1ySHyhh8I/t6AGy6d80H5nsMKTMcWnbbOikLWXrU sCU9V8hHs+GJ9jkGGhv6XlkPZFPAoDCH3YUSL0OfwDPHiJiLmgmZrVOaCBoOa/npjTnS xqPp6RbG0jN/G2FkZcaJ3zzhcX/LKN9MDHMzRtl01OolITw0EdEJ2eNHAH5AXsnG72os AftTSd3yluEUuUFOxJJlfBnLjTyy0/lqVxuuzh8DZh5uF6ifFn4ltc9SLIbEIyoIcf2o DJlT24Swkz7rGYVjuMTIrhfRjd9CKx8zuo60DpLOR/VJ5tkeyCjx2EaDWTlyk1bSRC8z xGtQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:in-reply-to:content-disposition:mime-version :references:message-id:subject:cc:to:from:date:dkim-signature; bh=HIRvcwlSl4Hp1A2rT9yMEOxIWfhwKnmROPnxOG/25YE=; b=ANsrB5MYa3NZE1tdJ3UINxisnEsMcdun8CuR2pAO1mJ8lnC1kfwksPFRzTzpUa1kWT ZGUN2ru8CRI1vQ2pQE+Q1MZkLcRUL4n1pmCTjyhQbcFDAtNmu7jB4iC95ws+P7k2R4bF 1AUpYAKbV+MPy4t/9hcXadhTE1Q7ASsLsd0h39ZepPNLb72x5PKvBENMbGWogUA3/JHc /YOfeHCkh3IcKB8GlCrT990vWTS7JOouXJ15UmEiColrFf33FS1FBycK1iVQB3KGd7Lz WO1ahAuA1z50xn36VAeJjNVcf24Q1D56dfNTwgoGEjycHFlKC8rFpkwKWacu2vWckdu5 TY1Q== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@infradead.org header.s=casper.20170209 header.b=MLdEMXb4; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id b6si4205727ede.282.2022.01.14.14.08.35; Fri, 14 Jan 2022 14:08:59 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=casper.20170209 header.b=MLdEMXb4; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239144AbiANPRk (ORCPT + 99 others); Fri, 14 Jan 2022 10:17:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33952 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242585AbiANPR0 (ORCPT ); Fri, 14 Jan 2022 10:17:26 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4FC8DC06173F; Fri, 14 Jan 2022 07:17:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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; bh=HIRvcwlSl4Hp1A2rT9yMEOxIWfhwKnmROPnxOG/25YE=; b=MLdEMXb4SCvNvAol4jQBhoZrDw ls0LbGXaMsBPr5myQwSrS7mm891UDbP7d0aB9f4apmNBECNtiID+VWfx52VHds1RymMbnwNkWl3UZ uXqRMmCE7eCW15t3NcyRYgr40FR9PAbyMpDMKo+4VVqlAo6j3Za51gppGoB6xxlmWLgexYnbKyFOX FQssGbBTPx6anq/Gxt2YEa+gHIqTTeO/DpsQLsAiLPvbwHucX3ZFedtzFE04M0xVHMJJmtGuB3QtZ 0YORWbZUwdCE60GdjX4gvo5ZhMwkhQ84SmqyNXAk5H+iQhQdIYyGA07EH7KLCc24+jKSIgsY3CCIQ wGoiQw4g==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1n8OK0-005tS8-Ou; Fri, 14 Jan 2022 15:16:57 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id D88AD3002C1; Fri, 14 Jan 2022 16:16:53 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id B4C2923CDA75B; Fri, 14 Jan 2022 16:16:53 +0100 (CET) Date: Fri, 14 Jan 2022 16:16:53 +0100 From: Peter Zijlstra To: Peter Oskolkov Cc: mingo@redhat.com, tglx@linutronix.de, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, x86@kernel.org, pjt@google.com, posk@google.com, avagin@google.com, jannh@google.com, tdelisle@uwaterloo.ca Subject: Re: [RFC][PATCH 3/3] sched: User Mode Concurency Groups Message-ID: References: <20211214204445.665580974@infradead.org> <20211214205358.701701555@infradead.org> <20211221171900.GA580323@dev-hv> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 14, 2022 at 03:09:55PM +0100, Peter Zijlstra wrote: > > I think the assumption is based on the idea that a process > > using UMCG will get affined to N CPUs, will have N servers and > > a number of workers, and they will all happily cooperate and not > > get any extra threads running. > > > > Of course the pretty picture was not completely true, as the unblocked > > tasks do consume extra threads in the kernel, though never in the > > userspace. > > Right, there is some unmanaged time anyway. Also, since we force wake to the same CPU, and overlapping runtime is 'short', they should all stick to the same CPU, even if we don't pin.