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 2115CC433F5 for ; Fri, 26 Nov 2021 21:11:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8FCDB6B0075; Fri, 26 Nov 2021 16:11:30 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 8828E6B0078; Fri, 26 Nov 2021 16:11:30 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 724946B007B; Fri, 26 Nov 2021 16:11:30 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0129.hostedemail.com [216.40.44.129]) by kanga.kvack.org (Postfix) with ESMTP id 5F2D46B0075 for ; Fri, 26 Nov 2021 16:11:30 -0500 (EST) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 22204184EBCFC for ; Fri, 26 Nov 2021 21:11:20 +0000 (UTC) X-FDA: 78852327120.06.32C1DAB Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by imf17.hostedemail.com (Postfix) with ESMTP id A6A0DF0001EA for ; Fri, 26 Nov 2021 21:11:19 +0000 (UTC) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1637961078; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=5gCM9kEhWoUkGOuKC2Aj4uPDGmWdwYkbfbhcTqi7DsY=; b=me44102yT0NMUViVyLMC06slnSGgufjN36cbpUgHj6rkyn+3p009+lPwTqrGdqulrdfRA+ 9h1//zwZq9b1+o+L5w6kVvA3r2r3+3yFg8IcSCNDJEo6AOcegcys7W9UGjGODXxywi/a9z afu31jyItoNBrE0HQg5EfoYyVSFNfu0gRGHsOT8vccyRwPkX6tAfduaKXkvWA6apkMEEc0 CsioqYu+xcIA64n2xmjRRvsTJsfQJmLnLxyHQcFE7D7WAUdf8W0kJrQPM7x2ymYsLPU7qo Gr1zuy5UOQtvPDiVFoVsd+LuR48wn+0l5pbnzujo4aAqJNDipDHo9QSSI/u9IA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1637961078; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=5gCM9kEhWoUkGOuKC2Aj4uPDGmWdwYkbfbhcTqi7DsY=; b=RcHGvoHf5TfyyVW+fZX/Y4s635PSzKqB8O4YXbPhwUGL6QkOYegpmZfdJDuExMRuk1KW1Y SV/ifilsxWdczVCw== To: Peter Zijlstra , Peter Oskolkov Cc: 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 In-Reply-To: <20211124211927.GG721624@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> Date: Fri, 26 Nov 2021 22:11:17 +0100 Message-ID: <877dcuhbbe.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: A6A0DF0001EA X-Stat-Signature: fjzijjc7c4cb4mcntudhyqm3wpqxn7dx Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=linutronix.de header.s=2020 header.b=me44102y; dkim=pass header.d=linutronix.de header.s=2020e header.b=RcHGvoHf; spf=pass (imf17.hostedemail.com: domain of tglx@linutronix.de designates 193.142.43.55 as permitted sender) smtp.mailfrom=tglx@linutronix.de; dmarc=pass (policy=none) header.from=linutronix.de X-HE-Tag: 1637961079-222167 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 Wed, Nov 24 2021 at 22:19, Peter Zijlstra wrote: > On Mon, Nov 22, 2021 at 01:13:24PM -0800, Peter Oskolkov wrote: > >> + * Timestamp: a 46-bit CLOCK_MONOTONIC timestamp, at 16ns resolution. > >> +static int umcg_update_state(u64 __user *state_ts, u64 *expected, u64 desired, >> + bool may_fault) >> +{ >> + u64 curr_ts = (*expected) >> (64 - UMCG_STATE_TIMESTAMP_BITS); >> + u64 next_ts = ktime_get_ns() >> UMCG_STATE_TIMESTAMP_GRANULARITY; > > I'm still very hesitant to use ktime (fear the HPET); but I suppose it > makes sense to use a time base that's accessible to userspace. Was > MONOTONIC_RAW considered? MONOTONIC_RAW is not really useful as you can't sleep on it and it won't solve the HPET crap either. Thanks, tglx