Re: [RFC][PATCH 2/7] UBC: core (structures, API)

[Rohit Seth <rohitseth@google.com>]

On Thu, 2006-08-17 at 15:53 +0400, Kirill Korotaev wrote:
> Rohit Seth wrote:
> > On Wed, 2006-08-16 at 19:37 +0400, Kirill Korotaev wrote:
> > 
> >>Core functionality and interfaces of UBC:
> >>find/create beancounter, initialization,
> >>charge/uncharge of resource, core objects' declarations.
> >>
> >>Basic structures:
> >>  ubparm           - resource description
> >>  user_beancounter - set of resources, id, lock
> >>
> >>Signed-Off-By: Pavel Emelianov <xemul@sw.ru>
> >>Signed-Off-By: Kirill Korotaev <dev@sw.ru>
> >>
> >>---
> >> include/ub/beancounter.h |  157 ++++++++++++++++++
> >> init/main.c              |    4
> >> kernel/Makefile          |    1
> >> kernel/ub/Makefile       |    7
> >> kernel/ub/beancounter.c  |  398 +++++++++++++++++++++++++++++++++++++++++++++++
> >> 5 files changed, 567 insertions(+)
> >>
> >>--- /dev/null	2006-07-18 14:52:43.075228448 +0400
> >>+++ ./include/ub/beancounter.h	2006-08-10 14:58:27.000000000 +0400
> >>@@ -0,0 +1,157 @@
> >>+/*
> >>+ *  include/ub/beancounter.h
> >>+ *
> >>+ *  Copyright (C) 2006 OpenVZ. SWsoft Inc
> >>+ *
> >>+ */
> >>+
> >>+#ifndef _LINUX_BEANCOUNTER_H
> >>+#define _LINUX_BEANCOUNTER_H
> >>+
> >>+/*
> >>+ *	Resource list.
> >>+ */
> >>+
> >>+#define UB_RESOURCES	0
> >>+
> >>+struct ubparm {
> >>+	/*
> >>+	 * A barrier over which resource allocations are failed gracefully.
> >>+	 * e.g. if the amount of consumed memory is over the barrier further
> >>+	 * sbrk() or mmap() calls fail, the existing processes are not killed.
> >>+	 */
> >>+	unsigned long	barrier;
> >>+	/* hard resource limit */
> >>+	unsigned long	limit;
> >>+	/* consumed resources */
> >>+	unsigned long	held;
> >>+	/* maximum amount of consumed resources through the last period */
> >>+	unsigned long	maxheld;
> >>+	/* minimum amount of consumed resources through the last period */
> >>+	unsigned long	minheld;
> >>+	/* count of failed charges */
> >>+	unsigned long	failcnt;
> >>+};
> > 
> > 
> > What is the difference between barrier and limit. They both sound like
> > hard limits.  No?
> check __charge_beancounter_locked and severity.
> It provides some kind of soft and hard limits.
> 

Would be easier to just rename them as soft and hard limits...

> >>+
> >>+/*
> >>+ * Kernel internal part.
> >>+ */
> >>+
> >>+#ifdef __KERNEL__
> >>+
> >>+#include <linux/config.h>
> >>+#include <linux/spinlock.h>
> >>+#include <linux/list.h>
> >>+#include <asm/atomic.h>
> >>+
> >>+/*
> >>+ * UB_MAXVALUE is essentially LONG_MAX declared in a cross-compiling safe form.
> >>+ */
> >>+	/* resources statistics and settings */
> >>+	struct ubparm		ub_parms[UB_RESOURCES];
> >>+};
> >>+
> > 
> > 
> > I presume UB_RESOURCES value is going to change as different resources
> > start getting tracked.
> what's wrong with it?
> 

...just that user land will need to be some how informed about that.

> > I think something like configfs should be used for user interface.  It
> > automatically presents the right interfaces to user land (based on
> > kernel implementation).  And you wouldn't need any changes in glibc etc.
> 1. UBC doesn't require glibc modificatins.

You are right not for setting the limits.  But for adding any new
functionality related to containers....as in you just added a new system
call to get the limits.

> 2. if you think a bit more about it, adding UB parameters doesn't
>    require user space changes as well.
> 3. it is possible to add any kind of interface for UBC. but do you like the idea
>    to grep 200(containers)x20(parameters) files for getting current usages?

How are you doing it currently and how much more efficient it is in
comparison to configfs?

>    Do you like the idea to convert numbers to strings and back w/o
>    thinking of data types?

IMO, setting up limits and containers (themselves) is not a common
operation.    I wouldn't be too worried about loosing those few extra
cycles in setting them up.

-rohit