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

[Kirill Korotaev]

Rohit Seth wrote:
> 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 at sw.ru>
>>>>Signed-Off-By: Kirill Korotaev <dev at 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.
the same way user space knows that system call is (not) implemented.
(include unistd.h :))) )

>>>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.
Do you state that glibc describes _all_ the existing system calls with some wrappers?

>>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?
currently it is done with a single file read.
you can grep it, sum up resources or do what ever you want from bash.
what is important! you can check whether container hits its limits
with a single command, while with configs you would have to look through
20 files...

IMHO it is convinient to have a text file representing the whole information state
and system call for applications.

>>   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.
it is not the question of performance...

Kirill