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Date:	Thu, 6 Mar 2014 13:07:52 +0300
From:	"Victor Miasnikov" <vvm@....by>
To:	<linux-kernel@...r.kernel.org>,
	"Brian Wong" <draconicpenguin1@...oo.com>
Cc:	"Abhishek Gupta \(LIS\)" <abgupta@...rosoft.com>,
	"KY Srinivasan" <kys@...rosoft.com>
Subject: Re: Linux does not use more than the startup RAM under Hyper-V with dynamic memory enabled RE: [PATCH 2/2] Drivers: hv: balloon: Online the hot-added memory "in context" Re: [PATCH 1/1] Drivers: hv:

Hi!

 Short:

 Question to Linux kernel team:

may be patch

>>> [PATCH 2/2] Drivers: hv: balloon: Online the hot-added memory "in context"

can solve problems with dynamic memory hot add in Hyper-V VMs with Linux OS ?



 Full:

BW>> .., if I set the startup memory to 512 MB, and enable dynamic
BW>> memory with a minimum of 512 MB and a maximum of 8192 MB,
BW>>  the system will never allocate than 512 MB of physical memory

BW>>
BW>> Have I encountered a bug in the Hyper-V balloon driver?
BW>>

 Unfortunately,  It's long story . . . :-(

a)

 I already ( on January 09, 2014 2:18 PM )  write about problems with "Online the hot-added memory"  in "user space" see
P.P.S.

b)

  See

Bug 979257 -[Hyper-V][RHEL6.5][RFE]in-kernel online support for memory hot-add
https://bugzilla.redhat.com/show_bug.cgi?id=979257

 (  Info from this topic may be interessant not only for RedHat users )


b2)

 Detail about pathes related problem "Online the hot-added memory"  in "user space" :

>>> [PATCH 2/2] Drivers: hv: balloon: Online the hot-added memory "in context"
>>>
>>>
>>> === 0001-Drivers-base-memory-Export-functionality-for-in-kern.patch
>>>  . . .
>>> +/*
>>> + * Given the start pfn of a memory block; bring the memory
>>> + * block online. This API would be useful for drivers that may
>>> + * want to bring "online" the memory that has been hot-added.
>>> + */
>>> +
>>> +int online_memory_block(unsigned long start_pfn) {  struct mem_section
>>> +*cur_section;  struct memory_block *cur_memory_block;
>>>
>>>  . . .
>>> ===
>>>
>>>
>>> ==
>>>  . . .
>>> == 0002-Drivers-hv-balloon-Online-the-hot-added-memory-in-co.patch
>>>   . . .
>>>    /*
>>> -   * Wait for the memory block to be onlined.
>>> -   * Since the hot add has succeeded, it is ok to
>>> -   * proceed even if the pages in the hot added region
>>> -   * have not been "onlined" within the allowed time.
>>> +   * Before proceeding to hot add the next segment,
>>> +   * online the segment that has been hot added.
>>>     */
>>> -  wait_for_completion_timeout(&dm_device.ol_waitevent, 5*HZ);
>>> +  online_memory_block(start_pfn);
>>>
>>>   }




c)

  Before apply patches ( see in P.S. about native udev-script) we are need use one of this methods:

http://social.technet.microsoft.com/Forums/en-US/8e1994b9-9ca1-4411-ad8e-25e6b1ee28e1/dynamic-memory-on-linux-vm?forum=linuxintegrationservices



c1)

"/bin/cp method" by Nikolay Pushkarev :

Following udev rule works slightly faster for me (assuming that memory0 bank always in online state):

SUBSYSTEM=="memory", ACTION=="add", DEVPATH=="/devices/system/memory/memory[1-9]*",
RUN+="/bin/cp /sys$devpath/../memory0/state /sys$devpath/state"}}

( VVM : of course all need be place in one line, 2 line in this msg. -- only for good visual formating reasons )


c2)

udev rule using "putarg" by Nikolay Pushkarev :


 Even "/bin/cp method" udev rule work time to time not as need :-(


As a result, Nikolay Pushkarev write a program putarg.c, that is even faster than "/bin/cp method" :

==
#include <stdio.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <string.h>
int main(int argc, char** argv) {
  int i, fd;
  if (argc < 2) return 0;
  if ((fd = open(argv[1], O_RDWR)) < 0) return 1;
  for (i = 2; i < argc; i++) {
    if (write(fd, argv[i], strlen(argv[i])) < 0) {
      close(fd);
      return i;
    }
  }
  close(fd);
  return 0;
}
==

 The first argument - the name of the output file ,
and argument number 2 ( and all subsequent (  if exist ) ) - are text that are wiil be written in output file.


 Compile source code to executable file by run command:
gcc -o putarg -s putarg.c

The resulting binary need be placed an accessible location , such as /usr/bin, or wherever you want.


Now udev rule using "putarg" can be written as :

SUBSYSTEM=="memory", ACTION=="add", RUN+="/usr/bin/putarg /sys$devpath/state online"


This complex solutions ( compiled file and udev-rule ) works exceptionally fast.





Best regards, Victor Miasnikov
Blog:  http://vvm.blog.tut.by/

P.S.

Nikolay Pushkarev about standart udev-script :

{{

Strange, that the native udev-script

SUBSYSTEM=="memory", ACTION=="add", ATTR{state}="online"


triggered somehow through time ( VVM: very often not work as need )


}}



P.P.S.

----- Original Message ----- 
From: "Victor Miasnikov"
To: "Dan Carpenter"; "K. Y. Srinivasan" ; <linux-kernel@...r.kernel.org>
Cc: "Greg KH" ; <devel@...uxdriverproject.org>; <olaf (at) aepfle.de>; ""Andy Whitcroft"" <zzzzzzzzzzzz (at)
canonical.com>;
<jasowang (at) redhat.com>
Sent: Thursday, January 09, 2014 2:18 PM
Subject: RE: [PATCH 2/2] Drivers: hv: balloon: Online the hot-added memory "in context" Re: [PATCH 1/1] Drivers: hv:
Implement the file copy service


Hi!

> Is there no way we could implement file copying in user space?


  For "file copy service"  "user space"  may be pretty good

But I ( and other Hyper-V sysadmin)  see non-Ok ( in "political correct" terminalogy) results with "hv: balloon: Online
the hot-added memory" in "user space"


==
 [PATCH 2/2] Drivers: hv: balloon: Online the hot-added memory "in context"
==


 What news?  Roadmap?


Best regards, Victor Miasnikov
Blog:  http://vvm.blog.tut.by/




P.P.S.

----- Original Message ----- 
From: "Brian Wong"
To: <linux-kernel@...r.kernel.org>
Sent: Thursday, March 06, 2014 9:24 AM
Subject: Re: Linux does not use more than the startup RAM under Hyper-V with dynamic memory enabled


On 3/6/2014 1:20 AM, Brian Wong wrote:

   . . .

> The kernel is built with the full set of Hyper-V drivers, including the
> key "Microsoft Hyper-V Balloon Driver" as well as memory hot-add and
> hot-remove functionality. This is happening with both the Gentoo-patched
> 3.10.32 kernel and the vanilla 3.12.5 kernel. The host machine has a
> total of 24 GB of memory.
>
> For now, I am working around the issue by starting the VM with the
> startup memory set to the maximum and letting Hyper-V take the usused
> memory back when it is not in use. The VM will then get the extra memory
> when it needs it.
>
> Have I encountered a bug in the Hyper-V balloon driver?
>

Just a correction: the vanilla kernel version is 3.13.5, not 3.12.5.
Sorry for any confusion.

-- 
Brian Wong
http://www.fierydragonlord.com
--



----- Original Message ----- 
From: "Brian Wong"
To: <linux-kernel@...r.kernel.org>
Sent: Thursday, March 06, 2014 9:20 AM
Subject: Linux does not use more than the startup RAM under Hyper-V with dynamic memory enabled

I'm new to LKML, so please don't be too hard on me :)

I'm running Gentoo Linux under Microsoft Client Hyper-V on Windows 8.1
Pro, and I've noticed some odd behavior with respect to dynamic memory
(aka memory ballooning). The system will never use more than the startup
memory defined in the virtual machine's settings.

( VVM: typewriting error viRtual fixed by me, for best search in future )

For example, if I set the startup memory to 512 MB, and enable dynamic
memory with a minimum of 512 MB and a maximum of 8192 MB, the system
will never allocate than 512 MB of physical memory, despite Hyper-V
assigning more memory to the VM and the added memory being visible in
the output of "free" and "htop". Attempting to use more memory causes
the system to start paging to swap, rather than actually allocating the
memory above the startup memory assigned to the VM.

The kernel is built with the full set of Hyper-V drivers, including the
key "Microsoft Hyper-V Balloon Driver" as well as memory hot-add and
hot-remove functionality. This is happening with both the Gentoo-patched
3.10.32 kernel and the vanilla 3.12.5 kernel. The host machine has a
total of 24 GB of memory.

(
  Brian Wong wrote On 3/6/2014 1:20 AM:
 Just a correction: the vanilla kernel version is 3.13.5, not 3.12.5. )
)

For now, I am working around the issue by starting the VM with the
startup memory set to the maximum and letting Hyper-V take the usused
memory back when it is not in use. The VM will then get the extra memory
when it needs it.

Have I encountered a bug in the Hyper-V balloon driver?

-- 
Brian Wong
http://www.fierydragonlord.com
--




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