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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3B136C433EF for ; Mon, 29 Nov 2021 22:23:14 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9822F6B006C; Mon, 29 Nov 2021 17:23:03 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 930286B0071; Mon, 29 Nov 2021 17:23:03 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7F7AB6B0073; Mon, 29 Nov 2021 17:23:03 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0135.hostedemail.com [216.40.44.135]) by kanga.kvack.org (Postfix) with ESMTP id 6E75B6B006C for ; Mon, 29 Nov 2021 17:23:03 -0500 (EST) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 299C5184B4AE6 for ; Mon, 29 Nov 2021 22:22:53 +0000 (UTC) X-FDA: 78863393784.05.6D3FF58 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf13.hostedemail.com (Postfix) with ESMTP id 88B6C1046291 for ; Mon, 29 Nov 2021 22:22:47 +0000 (UTC) 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=P+7rLpDmI0GB1uveawAKeTOyJh4WuhEPHuwGYT+nYA8=; b=TwmRukm9ui9hBITy8IFXrg6u+n pEYD+1yhOiTaaD/zRtr0G6JNDxz7aFt1dRouS3jONa0pV8lY369lo1UwDcuXjvWJwqOF8Ow5AwXrR vwqWZBre13UBT3muF3jwPbLaG5zmJa7J84p9xVISbAJxl+Q1Q7ic05yXJ1SKP67wdjXBB3IP+wiYd O8l8+Od6JPMkyTeGywiiTjGEjQmeYRCU5X40brTQi9cTBsff8ImI4ViGbcuv1kueyZ+UJU7+sw9U2 B7fGvtXxRc5rXHPKgvCfFpM1fzT+8zPrgafOyIzBv5qZtrCZAAitFJyDCRGg9/w9wAku3ZzJ2Mkxd C2Cdyv8w==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mrp2q-009SwH-6B; Mon, 29 Nov 2021 22:22:45 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id 1826D98675D; Mon, 29 Nov 2021 23:22:44 +0100 (CET) Date: Mon, 29 Nov 2021 23:22:43 +0100 From: Peter Zijlstra To: Thomas Gleixner Cc: Peter Oskolkov , Ingo Molnar , Andrew Morton , Dave Hansen , Andy Lutomirski , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Paul Turner , Ben Segall , Peter Oskolkov , Andrei Vagin , Jann Horn , Thierry Delisle Subject: Re: [PATCH v0.9.1 3/6] sched/umcg: implement UMCG syscalls Message-ID: <20211129222243.GR721624@worktop.programming.kicks-ass.net> References: <20211122211327.5931-1-posk@google.com> <20211122211327.5931-4-posk@google.com> <20211124211927.GG721624@worktop.programming.kicks-ass.net> <877dcuhbbe.ffs@tglx> <87r1ayd3as.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87r1ayd3as.ffs@tglx> X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 88B6C1046291 X-Stat-Signature: bez44umh9bwcrsfmokr1a1rrhhb6o6ad Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=TwmRukm9; dmarc=none; spf=none (imf13.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=peterz@infradead.org X-HE-Tag: 1638224567-983371 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Nov 29, 2021 at 11:07:07PM +0100, Thomas Gleixner wrote: > On Fri, Nov 26 2021 at 22:52, Peter Zijlstra wrote: > The size is the same, i.e. 1 bit per nanosecond :) :-) > > The only time that's relevant though is when you're going to mix these > > timestamps with CLOCK_THREAD_CPUTIME_ID, which might just be > > interesting. > > Uuurg. If you want to go towards CLOCK_THREAD_CPUTIME_ID, that's going > to be really nasty. Actually you can sleep on that clock, but that's a > completely different universe. If anything like that is desired then we > need to rewrite that posix CPU timer muck completely with all the bells > and whistels and race conditions attached to it. *Shudder* Oh, I wasn't thinking anything as terrible as that. Sleeping on that clock is fundamentally daft since it doesn't run when thats is sleeping, consider trying to sleep on your own runtime :-) I was only considering combining THREAD_CPUTIME timestamps with the UMCG timestamps to compute how much unmanaged time there was, or other such things. Anyway, lets forget I bought this up and assume that for practical purposes all [ns] are of equal length.