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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 58DEEC25B08 for ; Wed, 17 Aug 2022 19:21:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241471AbiHQTVX (ORCPT ); Wed, 17 Aug 2022 15:21:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40496 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241283AbiHQTVV (ORCPT ); Wed, 17 Aug 2022 15:21:21 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 459CB96FE9 for ; Wed, 17 Aug 2022 12:21:19 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id ADEC06148D for ; Wed, 17 Aug 2022 19:21:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0C92EC433C1; Wed, 17 Aug 2022 19:21:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1660764078; bh=CJkeJbx7uI1sta5bRVW113vyjtApFkiwjWdcCZ3nWF8=; h=Date:To:From:Subject:From; b=QM4T2SzwpSkPIAy5sOrXo5GzCJ32CXdVUAEHRFn8TOqK5+83ZomsCsIN/JDTGO3k6 XoR1GiN3ZSnuvE/KYsEIG+mCZKmRNiSYjFhXQx85lqNaPAKAPiVjHCRyUqflLGHU+F 3aTr/EWx0jHDW+28E1JKcyBE3ixtwLEVAjai+eNM= Date: Wed, 17 Aug 2022 12:21:17 -0700 To: mm-commits@vger.kernel.org, slyich@gmail.com, akpm@linux-foundation.org From: Andrew Morton Subject: + ia64-fix-clock_getreclock_monotonic-to-report-itc-frequency.patch added to mm-nonmm-unstable branch Message-Id: <20220817192118.0C92EC433C1@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: ia64: fix clock_getre(CLOCK_MONOTONIC) to report ITC frequency has been added to the -mm mm-nonmm-unstable branch. Its filename is ia64-fix-clock_getreclock_monotonic-to-report-itc-frequency.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/ia64-fix-clock_getreclock_monotonic-to-report-itc-frequency.patch This patch will later appear in the mm-nonmm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Sergei Trofimovich Subject: ia64: fix clock_getre(CLOCK_MONOTONIC) to report ITC frequency Date: Mon, 15 Aug 2022 06:49:44 +0100 clock_gettime(CLOCK_MONOTONIC, &tp) is very precise on ia64 as it uses ITC (similar to rdtsc on x86). It's not quite a hrtimer as it is a few times slower than 1ns. Usually 2-3ns. clock_getres(CLOCK_MONOTONIC, &res) never reflected that fact and reported 0.04s precision (1/HZ value). In https://bugs.gentoo.org/596382 gstreamer's test suite failed loudly when it noticed precision discrepancy. Before the change: clock_getres(CLOCK_MONOTONIC, &res) reported 250Hz precision. After the change: clock_getres(CLOCK_MONOTONIC, &res) reports ITC (400Mhz) precision. The patch is based on matoro's fix. It adds a bit of explanation why we need to special-case arch-specific clock_getres(). Link: https://lkml.kernel.org/r/20220815054944.4130786-1-slyich@gmail.com Signed-off-by: Sergei Trofimovich Signed-off-by: Andrew Morton --- arch/ia64/kernel/sys_ia64.c | 26 ++++++++++++++++++++++++ arch/ia64/kernel/syscalls/syscall.tbl | 2 - 2 files changed, 27 insertions(+), 1 deletion(-) --- a/arch/ia64/kernel/syscalls/syscall.tbl~ia64-fix-clock_getreclock_monotonic-to-report-itc-frequency +++ a/arch/ia64/kernel/syscalls/syscall.tbl @@ -240,7 +240,7 @@ 228 common timer_delete sys_timer_delete 229 common clock_settime sys_clock_settime 230 common clock_gettime sys_clock_gettime -231 common clock_getres sys_clock_getres +231 common clock_getres ia64_clock_getres 232 common clock_nanosleep sys_clock_nanosleep 233 common fstatfs64 sys_fstatfs64 234 common statfs64 sys_statfs64 --- a/arch/ia64/kernel/sys_ia64.c~ia64-fix-clock_getreclock_monotonic-to-report-itc-frequency +++ a/arch/ia64/kernel/sys_ia64.c @@ -166,3 +166,29 @@ ia64_mremap (unsigned long addr, unsigne force_successful_syscall_return(); return addr; } + +asmlinkage long +ia64_clock_getres(const clockid_t which_clock, struct __kernel_timespec __user *tp) +{ + /* + * ia64's clock_gettime() syscall is implemented as a vdso call + * fsys_clock_gettime(). Currently it handles only + * CLOCK_REALTIME and CLOCK_MONOTONIC. Both are based on + * 'ar.itc' counter which gets incremented at a constant + * frequency. It's usually 400MHz, ~2.5x times slower than CPU + * clock frequency. Which is almost a 1ns hrtimer, but not quite. + * + * Let's special-case these timers to report correct precision + * based on ITC frequency and not HZ frequency for supported + * clocks. + */ + switch (which_clock) { + case CLOCK_REALTIME: + case CLOCK_MONOTONIC: + s64 tick_ns = DIV_ROUND_UP(NSEC_PER_SEC, local_cpu_data->itc_freq); + struct timespec64 rtn_tp = ns_to_timespec64(tick_ns); + return put_timespec64(&rtn_tp, tp); + } + + return sys_clock_getres(which_clock, tp); +} _ Patches currently in -mm which might be from slyich@gmail.com are ia64-fix-clock_getreclock_monotonic-to-report-itc-frequency.patch