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

From: Kirill Korotaev
Date: Fri Aug 18 2006 - 07:09:58 EST

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@xxxxx>
Signed-Off-By: Kirill Korotaev <dev@xxxxx>

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
+ *
+ */
+ * 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 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...


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