From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751338AbcGMUzX (ORCPT ); Wed, 13 Jul 2016 16:55:23 -0400 Received: from mail-yw0-f170.google.com ([209.85.161.170]:33211 "EHLO mail-yw0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751160AbcGMUzJ (ORCPT ); Wed, 13 Jul 2016 16:55:09 -0400 Date: Wed, 13 Jul 2016 16:54:33 -0400 From: Tejun Heo To: Colin Cross Cc: John Stultz , Ingo Molnar , Peter Zijlstra , lkml , Dmitry Shmidt , Rom Lemarchand , Todd Kjos , Oleg Nesterov Subject: Re: Severe performance regression w/ 4.4+ on Android due to cgroup locking changes Message-ID: <20160713205433.GD29670@mtj.duckdns.org> References: <20160713182102.GJ4065@mtj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.6.1 (2016-04-27) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Wed, Jul 13, 2016 at 01:44:50PM -0700, Colin Cross wrote: > > Switching between foreground and background isn't a hot path. It's > > human initiated operations after all. It taking 80 msecs sure is > > problematic but I'm skeptical that this is from actual contention > > given that the only reader side holders are fork and exit paths. > > Slight correction here, we move tasks to the foreground cgroup and > back around binder IPC calls from foreground processes to background > processes, so it is significantly hotter than just human initiated > operations. Oh I see. That's extreme and you would be paying in terms of migration overhead. It really doesn't make sense to generally optimize for migration as that often translates directly to overhead in actual hot paths in various controllers. That said, I don't think it'd be too difficult to keep things acceptable for the android case. Thanks. -- tejun