From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751514AbaCSS2a (ORCPT ); Wed, 19 Mar 2014 14:28:30 -0400 Received: from mail-we0-f175.google.com ([74.125.82.175]:43341 "EHLO mail-we0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750801AbaCSS22 (ORCPT ); Wed, 19 Mar 2014 14:28:28 -0400 From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , Andrew Morton , Ingo Molnar , Jens Axboe , Kevin Hilman , "Paul E. McKenney" , Peter Zijlstra , Thomas Gleixner Subject: [RFC PATCH 0/3] nohz: Move nohz kick out of scheduler IPI Date: Wed, 19 Mar 2014 19:28:19 +0100 Message-Id: <1395253702-12489-1-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.8.3.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When a full dynticks CPU runs in single task mode then a new task gets enqueued, we notify it through an IPI such that it restarts its tick. The IPI used here is the scheduler IPI. There are a few reasons for that: it can be called when interrupts are disabled, it can be called concurrently... These properties altogether aren't offered by the IPI subsystem. Meanwhile, bloating that way the scheduler IPI with scheduler unrelated code is an abuse of this fast path. We certainly don't want to start a big kernel IPI (BKI, the new shiny piece of my collection of big kernel things aside the big kernel tick, the big reiserfs lock, ..). So this patchset adds a small helper to the IPI subsystem that allows to queue an IPI from interrupt disabled code and handles concurrent callers as well. Eventually the nohz kick gets converted to this new facility. Partly inspired by a suggestion from Peter Zijlstra. Comments? git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git nohz/ipi Thanks, Frederic --- Frederic Weisbecker (3): smp: Non busy-waiting IPI queue nohz: Move full nohz kick to its own IPI nohz: Use IPI implicit full barrier against rq->nr_running r/w include/linux/smp.h | 12 ++++++++++++ include/linux/tick.h | 2 ++ kernel/sched/core.c | 14 ++++++-------- kernel/sched/sched.h | 12 +++++++++--- kernel/smp.c | 24 ++++++++++++++++++++++++ kernel/time/tick-sched.c | 20 ++++++++++++++++++++ 6 files changed, 73 insertions(+), 11 deletions(-)