From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754761AbbCQRid (ORCPT ); Tue, 17 Mar 2015 13:38:33 -0400 Received: from mail-pa0-f43.google.com ([209.85.220.43]:36734 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753892AbbCQRic (ORCPT ); Tue, 17 Mar 2015 13:38:32 -0400 From: John Stultz To: lkml Cc: John Stultz , Daniel Thompson , Russell King , Will Deacon , Catalin Marinas , Thomas Gleixner , Stephen Boyd , Ingo Molnar , Peter Zijlstra Subject: [PATCH 0/5] Arch-generic sched_clock NMI safety and optimizations for -tip Date: Tue, 17 Mar 2015 10:38:21 -0700 Message-Id: <1426613906-19718-1-git-send-email-john.stultz@linaro.org> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ingo, Peter, Thomas, The following patches from Daniel extend the arch-generic sched_clock implementation so that it can be safely called from NMI (or FIQ on ARM) context. They also optimize the sched_clock logic to improve cache performance. I wanted to send them along so they could be queued in -tip for 4.1. >>From Daniel's last post: "The data cache profile of sched_clock() in both the original code and my previous patch was somewhere between 2 and 3 (64-byte) cache lines, depending on alignment of struct clock_data. After patching, the cache profile for the normal case should be a single cacheline. NMI safety was tested on i.MX6 with perf drowning the system in FIQs and using the perf handler to check that sched_clock() returned monotonic values. At the same time I forcefully reduced kt_wrap so that update_sched_clock() is being called at >1000Hz. Without the patches the above system is grossly unstable, surviving [9K,115K,25K] perf event cycles during three separate runs. With the patch I ran for over 9M perf event cycles before getting bored." I'm relaying these along because in the past I've queued and submitted arch-generic sched_clock.c changes from Stephen via Thomas, but I wanted to make sure this got a look from Ingo and Peter. In the future, I think Stephen is probably the right person to act as patch-catcher for the kernel/time/sched_clock.c file. But I think those changes should continue to be merged in via the -tip tree w/ other scheduler code. Let me know if you have any objections or concerns. thanks -john Cc: Daniel Thompson Cc: Russell King Cc: Will Deacon Cc: Catalin Marinas Cc: Thomas Gleixner Cc: Stephen Boyd Cc: Ingo Molnar Cc: Peter Zijlstra These patches can also be pulled from the pull request below. The following changes since commit c517d838eb7d07bbe9507871fab3931deccff539: Linux 4.0-rc1 (2015-02-22 18:21:14 -0800) are available in the git repository at: https://git.linaro.org/people/john.stultz/linux.git fortglx/4.1/schedclock for you to fetch changes up to 4bb74b85d2e74cfec9e21a6de44b232a2983bcc7: sched_clock: Avoid deadlock during read from NMI (2015-03-10 20:28:58 -0700) ---------------------------------------------------------------- Daniel Thompson (5): sched_clock: Match scope of read and write seqcounts sched_clock: Optimize cache line usage sched_clock: Remove suspend from clock_read_data sched_clock: Remove redundant notrace from update function sched_clock: Avoid deadlock during read from NMI kernel/time/sched_clock.c | 195 ++++++++++++++++++++++++++++++++-------------- 1 file changed, 138 insertions(+), 57 deletions(-) -- 1.9.1