Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753431AbbGFPd5 (ORCPT ); Mon, 6 Jul 2015 11:33:57 -0400 Received: from mail-wi0-f172.google.com ([209.85.212.172]:34970 "EHLO mail-wi0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750862AbbGFPdy (ORCPT ); Mon, 6 Jul 2015 11:33:54 -0400 From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , Oleg Nesterov , Christoph Lameter , Rik van Riel , Andrew Morton Subject: [PATCH 0/3] kmod: Make nohz-full friendly + cleanups Date: Mon, 6 Jul 2015 17:33:38 +0200 Message-Id: <1436196821-13962-1-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 2.1.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1621 Lines: 39 Usermodehelpers kernel threads are nohz-full unfriendly because they force some explicit CPU-wide affinity that happen to disturb user code that don't want to see noise on isolated CPUs. So I spent many time on that, despite the one-liner end result. The out-of-date comments didn't help much, especially it wasn't clear why we need khelper at all, probably it was first introduced to bring necessary asynchronous code but I couldn't justify that with the current code. I wrote patches to remove it but finally realized we still need it to inherit a system wide (or nohz-full housekeeping) CPU affinity on usermodehelper kernel threads because some usermodehelper callers may have a reduced affinity (eg: per cpu workqueues). All I needed eventually was to improve the comments to highlight that purpose. And remove a nohz-full unfriendly wide affinity forcing. git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git nohz/kmod HEAD: 9a0ad418b7739fbbe4add684551aa5582a58718b Thanks, Frederic --- Frederic Weisbecker (3): kmod: Bunch of internal functions renames kmod: Add up-to-date explanations on the purpose of each asynchronous levels kmod: Remove unecessary explicit wide CPU affinity setting kernel/kmod.c | 61 +++++++++++++++++++++++++++++++++++++++++------------------ 1 file changed, 43 insertions(+), 18 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/