From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756035Ab1BCJlm (ORCPT ); Thu, 3 Feb 2011 04:41:42 -0500 Received: from shutemov.name ([188.40.19.243]:53059 "EHLO shutemov.name" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755397Ab1BCJlk (ORCPT ); Thu, 3 Feb 2011 04:41:40 -0500 Date: Thu, 3 Feb 2011 11:41:38 +0200 From: "Kirill A. Shutemov" To: Matt Helsley Cc: Paul Menage , Li Zefan , containers@lists.linux-foundation.org, jacob.jun.pan@linux.intel.com, Arjan van de Ven , linux-kernel@vger.kernel.org Subject: Re: [PATCH, v3 2/2] cgroups: introduce timer slack subsystem Message-ID: <20110203094138.GD1083@shutemov.name> References: <1296679656-31163-1-git-send-email-kirill@shutemov.name> <1296679656-31163-3-git-send-email-kirill@shutemov.name> <20110203054616.GT16432@count0.beaverton.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110203054616.GT16432@count0.beaverton.ibm.com> User-Agent: Mutt/1.5.20 (2010-08-04) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 02, 2011 at 09:46:16PM -0800, Matt Helsley wrote: > On Wed, Feb 02, 2011 at 10:47:36PM +0200, Kirill A. Shutsemov wrote: > > From: Kirill A. Shutemov > > > > Provides a way of tasks grouping by timer slack value. Introduces per > > cgroup max and min timer slack value. When a task attaches to a cgroup, > > its timer slack value adjusts (if needed) to fit min-max range. > > > > It also provides a way to set timer slack value for all tasks in the > > cgroup at once. > > > > This functionality is useful in mobile devices where certain background > > apps are attached to a cgroup and minimum wakeups are desired. > > > > Signed-off-by: Kirill A. Shutemov > > Idea-by: Jacob Pan > > --- > > include/linux/cgroup_subsys.h | 6 + > > include/linux/init_task.h | 4 +- > > init/Kconfig | 10 ++ > > kernel/Makefile | 1 + > > kernel/cgroup_timer_slack.c | 242 +++++++++++++++++++++++++++++++++++++++++ > > kernel/sys.c | 24 +++- > > 6 files changed, 280 insertions(+), 7 deletions(-) > > create mode 100644 kernel/cgroup_timer_slack.c > > > > diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h > > index ccefff0..e399228 100644 > > --- a/include/linux/cgroup_subsys.h > > +++ b/include/linux/cgroup_subsys.h > > @@ -66,3 +66,9 @@ SUBSYS(blkio) > > #endif > > > > /* */ > > + > > +#ifdef CONFIG_CGROUP_TIMER_SLACK > > +SUBSYS(timer_slack) > > +#endif > > + > > +/* */ > > diff --git a/include/linux/init_task.h b/include/linux/init_task.h > > index caa151f..48eca8f 100644 > > --- a/include/linux/init_task.h > > +++ b/include/linux/init_task.h > > @@ -124,6 +124,8 @@ extern struct cred init_cred; > > # define INIT_PERF_EVENTS(tsk) > > #endif > > > > +#define TIMER_SLACK_NS_DEFAULT 50000 > > + > > /* > > * INIT_TASK is used to set up the first task table, touch at > > * your own risk!. Base=0, limit=0x1fffff (=2MB) > > @@ -177,7 +179,7 @@ extern struct cred init_cred; > > .cpu_timers = INIT_CPU_TIMERS(tsk.cpu_timers), \ > > .fs_excl = ATOMIC_INIT(0), \ > > .pi_lock = __RAW_SPIN_LOCK_UNLOCKED(tsk.pi_lock), \ > > - .timer_slack_ns = 50000, /* 50 usec default slack */ \ > > + .timer_slack_ns = TIMER_SLACK_NS_DEFAULT, \ > > .pids = { \ > > [PIDTYPE_PID] = INIT_PID_LINK(PIDTYPE_PID), \ > > [PIDTYPE_PGID] = INIT_PID_LINK(PIDTYPE_PGID), \ > > diff --git a/init/Kconfig b/init/Kconfig > > index be788c0..f21b4ce 100644 > > --- a/init/Kconfig > > +++ b/init/Kconfig > > @@ -596,6 +596,16 @@ config CGROUP_FREEZER > > Provides a way to freeze and unfreeze all tasks in a > > cgroup. > > > > +config CGROUP_TIMER_SLACK > > + tristate "Timer slack cgroup subsystem" > > + help > > + Provides a way of tasks grouping by timer slack value. > > + Introduces per cgroup timer slack value which will override > > + the default timer slack value once a task is attached to a > > + cgroup. > > + It's useful in mobile devices where certain background apps > > + are attached to a cgroup and minimum wakeups are desired. > > Again -- I don't think "minimum" is the right choice of words here. Ok, I'll fix it. > > + > > config CGROUP_DEVICE > > bool "Device controller for cgroups" > > help > > diff --git a/kernel/Makefile b/kernel/Makefile > > index 353d3fe..0b60239 100644 > > --- a/kernel/Makefile > > +++ b/kernel/Makefile > > @@ -61,6 +61,7 @@ obj-$(CONFIG_BACKTRACE_SELF_TEST) += backtracetest.o > > obj-$(CONFIG_COMPAT) += compat.o > > obj-$(CONFIG_CGROUPS) += cgroup.o > > obj-$(CONFIG_CGROUP_FREEZER) += cgroup_freezer.o > > +obj-$(CONFIG_CGROUP_TIMER_SLACK) += cgroup_timer_slack.o > > obj-$(CONFIG_CPUSETS) += cpuset.o > > obj-$(CONFIG_CGROUP_NS) += ns_cgroup.o > > obj-$(CONFIG_UTS_NS) += utsname.o > > diff --git a/kernel/cgroup_timer_slack.c b/kernel/cgroup_timer_slack.c > > new file mode 100644 > > index 0000000..a343a50 > > --- /dev/null > > +++ b/kernel/cgroup_timer_slack.c > > @@ -0,0 +1,242 @@ > > +/* > > + * cgroup_timer_slack.c - control group timer slack subsystem > > + * > > + * Copyright Nokia Corparation, 2011 > > + * Author: Kirill A. Shutemov > > + * > > + * This program is free software; you can redistribute it and/or modify > > + * it under the terms of the GNU General Public License as published by > > + * the Free Software Foundation; either version 2 of the License, or > > + * (at your option) any later version. > > + * > > + * This program is distributed in the hope that it will be useful, > > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > > + * GNU General Public License for more details. > > + */ > > +#include > > +#include > > +#include > > +#include > > + > > +struct cgroup_subsys timer_slack_subsys; > > +struct timer_slack_cgroup { > > + struct cgroup_subsys_state css; > > + unsigned long min_slack_ns; > > + unsigned long max_slack_ns; > > +}; > > + > > +enum { > > + TIMER_SLACK_MIN, > > + TIMER_SLACK_MAX, > > +}; > > + > > +int dummy_timer_slack_check(struct task_struct *task, unsigned long slack_ns); > > The above should be "extern" shouldn't it? Also, I think there's a way > to eliminate it (more below). > > > +extern int (*timer_slack_check)(struct task_struct *task, > > + unsigned long slack_ns); > > + > > +static struct timer_slack_cgroup *cgroup_to_tslack_cgroup(struct cgroup *cgroup) > > +{ > > + struct cgroup_subsys_state *css; > > + > > + css = cgroup_subsys_state(cgroup, timer_slack_subsys.subsys_id); > > + return container_of(css, struct timer_slack_cgroup, css); > > +} > > + > > +static int cgroup_timer_slack_check(struct task_struct *task, > > + unsigned long slack_ns) > > nit: rename to cgroup_timer_slack_allowed() ? cgroup_is_timer_slack_allowed() ? > > +{ > > + struct cgroup_subsys_state *css; > > + struct timer_slack_cgroup *tslack_cgroup; > > + > > + css = task_subsys_state(task, timer_slack_subsys.subsys_id); > > + tslack_cgroup = container_of(css, struct timer_slack_cgroup, css); > > + > > + if (slack_ns < tslack_cgroup->min_slack_ns) > > + return -EPERM; > > + if (slack_ns > tslack_cgroup->max_slack_ns) > > + return -EPERM; > > + return 0; > > +} > > + > > +static struct cgroup_subsys_state * > > +tslack_cgroup_create(struct cgroup_subsys *subsys, struct cgroup *cgroup) > > +{ > > + struct timer_slack_cgroup *tslack_cgroup; > > + > > + tslack_cgroup = kmalloc(sizeof(*tslack_cgroup), GFP_KERNEL); > > + if (!tslack_cgroup) > > + return ERR_PTR(-ENOMEM); > > + > > + if (cgroup->parent) { > > + struct timer_slack_cgroup *parent; > > + parent = cgroup_to_tslack_cgroup(cgroup->parent); > > + tslack_cgroup->min_slack_ns = parent->min_slack_ns; > > + tslack_cgroup->max_slack_ns = parent->max_slack_ns; > > + } else { > > + tslack_cgroup->min_slack_ns = 0UL; > > + tslack_cgroup->max_slack_ns = ULONG_MAX; > > + } > > + > > + return &tslack_cgroup->css; > > +} > > + > > +static void tslack_cgroup_destroy(struct cgroup_subsys *subsys, > > + struct cgroup *cgroup) > > +{ > > + kfree(cgroup_to_tslack_cgroup(cgroup)); > > +} > > + > > +/* > > + * Adjust ->timer_slack_ns and ->default_max_slack_ns of the task to fit > > + * limits of the cgroup. > > + */ > > +static void tslack_adjust_task(struct timer_slack_cgroup *tslack_cgroup, > > + struct task_struct *tsk) > > +{ > > + if (tslack_cgroup->min_slack_ns > tsk->timer_slack_ns) > > + tsk->timer_slack_ns = tslack_cgroup->min_slack_ns; > > + else if (tslack_cgroup->max_slack_ns < tsk->timer_slack_ns) > > + tsk->timer_slack_ns = tslack_cgroup->max_slack_ns; > > + > > + if (tslack_cgroup->min_slack_ns > tsk->default_timer_slack_ns) > > + tsk->default_timer_slack_ns = tslack_cgroup->min_slack_ns; > > + else if (tslack_cgroup->max_slack_ns < tsk->default_timer_slack_ns) > > + tsk->default_timer_slack_ns = tslack_cgroup->max_slack_ns; > > +} > > + > > +static void tslack_cgroup_attach(struct cgroup_subsys *subsys, > > + struct cgroup *cgroup, struct cgroup *prev, > > + struct task_struct *tsk, bool threadgroup) > > +{ > > + tslack_adjust_task(cgroup_to_tslack_cgroup(cgroup), tsk); > > +} > > + > > +static int tslack_write_set_slack_ns(struct cgroup *cgroup, struct cftype *cft, > > + u64 val) > > +{ > > + struct timer_slack_cgroup *tslack_cgroup; > > + struct cgroup_iter it; > > + struct task_struct *task; > > + > > + tslack_cgroup = cgroup_to_tslack_cgroup(cgroup); > > + if (!val || val < tslack_cgroup->min_slack_ns || > > Why is a val of 0 disallowed? I know having slack is good, but for > an administrator or tool that doesn't care about number of wakeups > and cares more about wringing out performance a slack of > 0 seems acceptable. Is this just here to be consistent with the > values passed in via prctl? Yes, it's to consistent with the prctl(). I don't think that it's good idea to allow to set timer_slack outside of range prctl() allows. It may lead to interface abuse. > > + val > tslack_cgroup->max_slack_ns ) > > + return -EINVAL; > > Shouldn't it be EPERM and not EINVAL? > > The write(2) man page says: "Other errors may occur, depending on the > object connected to fd." So I think EPERM is fine and more descriptive. What do you think about -EINVAL for (val == 0) and -EPERM for rest? > > + > > + /* Change timer slack value for all tasks in the cgroup */ > > + cgroup_iter_start(cgroup, &it); > > + while ((task = cgroup_iter_next(cgroup, &it))) > > + task->timer_slack_ns = val; > > + cgroup_iter_end(cgroup, &it); > > + > > + return 0; > > +} > > + > > +static u64 tslack_read_range(struct cgroup *cgroup, struct cftype *cft) > > +{ > > + struct timer_slack_cgroup *tslack_cgroup; > > + > > + tslack_cgroup = cgroup_to_tslack_cgroup(cgroup); > > + switch (cft->private) { > > + case TIMER_SLACK_MIN: > > + return tslack_cgroup->min_slack_ns; > > + case TIMER_SLACK_MAX: > > + return tslack_cgroup->max_slack_ns; > > + default: > > + BUG(); > > + }; > > +} > > + > > +static int tslack_write_range(struct cgroup *cgroup, struct cftype *cft, > > + u64 val) > > +{ > > + struct timer_slack_cgroup *tslack_cgroup; > > + struct cgroup_iter it; > > + struct task_struct *task; > > + > > + if (!val) > > + return -EINVAL; > > Same question re: 0 slack... > > > + > > + tslack_cgroup = cgroup_to_tslack_cgroup(cgroup); > > + switch (cft->private) { > > + case TIMER_SLACK_MIN: > > + if (val > tslack_cgroup->max_slack_ns) > > + return -EINVAL; > > + tslack_cgroup->min_slack_ns = val; > > + break; > > + case TIMER_SLACK_MAX: > > + if (val < tslack_cgroup->min_slack_ns) > > + return -EINVAL; > > + tslack_cgroup->max_slack_ns = val; > > + break; > > + default: > > + BUG(); > > + } > > + > > + /* > > + * Adjust timer slack value for all tasks in the cgroup to fit > > + * min-max range. > > + */ > > + cgroup_iter_start(cgroup, &it); > > + while ((task = cgroup_iter_next(cgroup, &it))) > > + tslack_adjust_task(tslack_cgroup, task); > > + cgroup_iter_end(cgroup, &it); > > + > > + return 0; > > +} > > + > > +static struct cftype files[] = { > > + { > > + .name = "set_slack_ns", > > + .write_u64 = tslack_write_set_slack_ns, > > + }, > > + { > > + .name = "min_slack_ns", > > + .private = TIMER_SLACK_MIN, > > + .read_u64 = tslack_read_range, > > + .write_u64 = tslack_write_range, > > + }, > > + { > > + .name = "max_slack_ns", > > + .private = TIMER_SLACK_MAX, > > + .read_u64 = tslack_read_range, > > + .write_u64 = tslack_write_range, > > + }, > > +}; > > Looks good, thanks! > > > + > > +static int tslack_cgroup_populate(struct cgroup_subsys *subsys, > > + struct cgroup *cgroup) > > +{ > > + return cgroup_add_files(cgroup, subsys, files, ARRAY_SIZE(files)); > > +} > > + > > +struct cgroup_subsys timer_slack_subsys = { > > + .name = "timer_slack", > > + .module = THIS_MODULE, > > +#ifdef CONFIG_CGROUP_TIMER_SLACK > > + .subsys_id = timer_slack_subsys_id, > > +#endif > > Uhh... why is the #ifdef necessary? Won't it always be true if we're > compiling this file? Try to compile it as module. ;) > > + .create = tslack_cgroup_create, > > + .destroy = tslack_cgroup_destroy, > > + .attach = tslack_cgroup_attach, > > + .populate = tslack_cgroup_populate, > > +}; > > + > > +static int __init init_cgroup_timer_slack(void) > > +{ > > + BUG_ON(timer_slack_check != dummy_timer_slack_check); > > You could just save the old timer_slack_check value into a static pointer > and then restore it in exit_cgroup_timer_slack. That would eliminate the > need for one of the two EXPORTs below but you wouldn't be able to do this > BUG_ON check. I think that'd be a slight improvement. > > > + timer_slack_check = cgroup_timer_slack_check; > > + return cgroup_load_subsys(&timer_slack_subsys); > > Shouldn't you load the subsystem first then set the timer_slack_check > function pointer once you know that the load has succeeded? I'll rework this part. Thanks for reviewing. -- Kirill A. Shutemov