VSwap - Revision history

Finist: vswap in vz7 details added

2020-07-17T15:57:27Z

vswap in vz7 details added

Kir: /* Convert non-VSwap CT to VSwap */ add a script

2013-10-02T00:02:34Z

‎Convert non-VSwap CT to VSwap: add a script

Kir: /* Implicit UBC parameters */ enlarge a bit

2013-10-01T23:24:19Z

‎Implicit UBC parameters: enlarge a bit

Kir: added a section name

2013-10-01T20:45:20Z

added a section name

Kir: Add /* Implicit UBC parameters */

2013-10-01T20:44:47Z

Add ‎Implicit UBC parameters

Kir: reformatting

2013-06-25T20:45:54Z

reformatting

Kir: /* See also */ fix extra ]

2013-06-25T20:41:42Z

‎See also: fix extra ]

Kir: /* See also */ fixed article name

2013-06-25T20:26:02Z

‎See also: fixed article name

Kir: /* See also */ link to another acticle in blog

2013-06-25T20:24:53Z

‎See also: link to another acticle in blog

Kir: improved

2013-06-18T01:00:57Z

improved

← Older revision		Revision as of 15:57, 17 July 2020
Line 96:		Line 96:

	In addition, vzctl checks if kernel support vswap, and refuses to start a vswap-enabled container on a non vswap capable kernel. The check is presence of <code>/proc/vz/vswap</code> file.		In addition, vzctl checks if kernel support vswap, and refuses to start a vswap-enabled container on a non vswap capable kernel. The check is presence of <code>/proc/vz/vswap</code> file.
		+
		+	== Details about vSwap implementation in Virtuozzo 7 ==
		+
		+	The Container swapping process is similar to that on a standalone computer.<br>
		+	This means in particular that some pages may get into the swap even if there is some free memory reported in the Container.<br>
		+	This may validly happen in case kernel memory management system detects some anonymous memory which is not touched for a long time by Container processes and decides that it's more
		+	efficient to put these anonymous pages into the swap and use more caches in a Container instead.
		+
		+	The Container swap space resides in physical node swap file.<br>
		+	When the swap-out for a Container starts, appropriate number of pages are allocated in physical swap on the host. Next
		+	# if there is no free memory on the host, the real swap-out of Container's memory to physical swap happens
		+	# if there is free memory on the host, the Container's memory is saved in a special swap cache in host's RAM and no real write to host's physical swap occurs
		+
		+	{{Note\|The physical swap space is allocated in both cases anyway, this guarantees all amount of host's swap cache for Containers memory can be written into physical swap on host in case the host gets short of RAM.}}
		+
		+	* '''Consequence 1''': without any configured node swap file the Container's `SWAPPAGES` parameter will be ignored.
		+
		+	* '''Consequence 2''': if node's swap size is less than sum of all Containers' swap sizes on the node, Containers won't be able to use 100% of their swap simultaneously - similar to RAM settings.

	== See also ==		== See also ==

@@ Line 76: / Line 76: @@
 # Add PHYSPAGES and SWAPPAGES parameters to config. Easiest way is to use <code>vzctl set $CTID --ram N --swap M --save</code>
-Now your config is vswap enabled, and when you (re)start it, vswap mechanism will be used by the kernel for this CT.
+Now your config is vswap enabled, and when you (re)start it (or use <code>--reset_ub</code>), vswap mechanism will be used by the kernel for this CT.
 == How to distinguish between vswap and non-vswap configs? ==

@@ Line 35: / Line 35: @@
 Since vzctl 4.6, if some optional beancounters are not set, vzctl sets them implicitly,
-using ram and swap and, in case of privvmpages, a new parameter called '''VM overcommit'''.
+based on '''ram''' and '''swap''' settings.
 The following formulae are used:
@@ Line 45: / Line 45: @@
 <math>vmguarpages_{bar} = vmguarpages_{lim} = ram + swap</math>
-Also, if <math>vm\_overcommit</math> is set to non-zero:
+==== VM overcommit and privvmpages ====
 : <math>privvmpages_{bar} = privvmpages_{lim} = (ram + swap) \times vm\_overcommit</math>
-otherwise:
+If it is not set:
 : <math>privvmpages_{bar} = privvmpages_{lim} = \infty</math>

← Older revision		Revision as of 20:45, 1 October 2013
Line 1:		Line 1:
	'''New [[Download/kernel/rhel6\|RHEL6-based OpenVZ]] kernel''' has a new memory management model, which supersedes [[UBC\|User beancounters]]. It is called '''VSwap'''.		'''New [[Download/kernel/rhel6\|RHEL6-based OpenVZ]] kernel''' has a new memory management model, which supersedes [[UBC\|User beancounters]]. It is called '''VSwap'''.
		+
		+	== Primary parameters ==

	With VSwap, there are two required parameters: <code>ram</code> and <code>swap</code> (a.k.a. <code>physpages</code> and <code>swappages</code>). All the other beancounters become optional.		With VSwap, there are two required parameters: <code>ram</code> and <code>swap</code> (a.k.a. <code>physpages</code> and <code>swappages</code>). All the other beancounters become optional.

@@ Line 1: / Line 1: @@
 '''New [[Download/kernel/rhel6|RHEL6-based OpenVZ]] kernel''' has a new memory management model, which supersedes [[UBC|User beancounters]]. It is called '''VSwap'''.
-Now you can set two primary parameters: <code>ram</code> and <code>swap</code> (a.k.a. <code>physpages</code> and <code>swappages</code>), while all the other beancounters become secondary and optional.
+With VSwap, there are two required parameters: <code>ram</code> and <code>swap</code> (a.k.a. <code>physpages</code> and <code>swappages</code>). All the other beancounters become optional.
 * '''physpages'''
@@ Line 29: / Line 29: @@
 {{Note|swap used by a container can exceed <code>swappages.limit</code>, but is always within sum of <code>physpages.limit</code> and <code>swappages.limit</code>.}}
 == Setting ==
@@ Line 38: / Line 59: @@
   vzctl set 777 --ram 512M --swap 1G --save
-== Convert non-vswap CT to Vswap ==
+== Convert non-VSwap CT to VSwap ==
 If you have an existing container with usual UBC parameters set, and you want to convert this one into VSwap enabled config, here's what you need to do.

@@ Line 4: / Line 4: @@
 * '''physpages'''
-: This parameter sets the amount of fast physical memory (RAM) available to processes inside a container, in memory pages.
+: This parameter sets the amount of fast physical memory (RAM) available to processes inside a container, in memory pages. Currently (as of 042stab042 kernel) the user memory, the kernel memory and the page cache are accounted into <code>physpages</code>.
 : The <code>barrier</code> is ignored and should be set to 0, and the <code>limit</code> sets the limit.
 * '''ram'''
@@ Line 13: / Line 13: @@
 * '''swappages'''
 : This parameter sets the amount of "slower memory" (vswap) available to processes inside a container, in memory pages.
 : The <code>barrier</code> is ignored and should be set to 0, and the <code>limit</code> sets the limit.

@@ Line 56: / Line 56: @@
 == See also ==
-* [http://openvz.livejournal.com/39644.html On vSwap and 042stab04x kernel improvements]]
+* [http://openvz.livejournal.com/39644.html On vSwap and 042stab04x kernel improvements]
 * [http://openvz.livejournal.com/39765.html Recent improvements in vzctl]
 [[Category: UBC]]

@@ Line 1: / Line 1: @@
 '''New [[Download/kernel/rhel6|RHEL6-based OpenVZ]] kernel''' has a new memory management model, which supersedes [[UBC|User beancounters]]. It is called '''VSwap'''.
-Now you can set two primary parameters: <code>physpages</code> and <code>swappages</code>, while all the other beancounters become secondary and optional.
+Now you can set two primary parameters: <code>ram</code> and <code>swap</code> (a.k.a. <code>physpages</code> and <code>swappages</code>), while all the other beancounters become secondary and optional.
 * '''physpages'''
-: This parameter limits the physical memory (RAM) available to processes inside a container.
+: This parameter sets the amount of fast physical memory (RAM) available to processes inside a container, in memory pages.
 : The <code>barrier</code> is ignored and should be set to 0, and the <code>limit</code> sets the limit.
 : Currently (as of >= 042stab042) the user memory, the kernel memory and the page cache are accounted into <code>physpages</code>.
 * '''swappages'''
-: This parameter limits the amount of swap space which can be used for processes inside a container.
+: This parameter sets the amount of "slower memory" (vswap) available to processes inside a container, in memory pages.
 : The <code>barrier</code> is ignored and should be set to 0, and the <code>limit</code> sets the limit.
 The sum of <code>physpages.limit</code> and <code>swappages.limit</code> limits the maximum amount
-of allocated memory which can be used by a container. When physpages limit
+of memory which can be used by a container. When physpages limit
 is reached, memory pages belonging to the container are pushed out to
 so called virtual swap (''vswap''). The difference between normal swap
@@ Line 20: / Line 26: @@
 swapping. Actual swap out occurs only if there is a global memory shortage
 on the system.
 == Setting ==
@@ Line 28: / Line 36: @@
   vzctl set 777 --ram 512M --swap 1G --save
 == Convert non-vswap CT to Vswap ==
@@ Line 46: / Line 49: @@
 == How to distinguish between vswap and non-vswap configs? ==
-Both <code>vzctl</code> and the kernel treats a configuration file as vswap one if PHYSPAGES limit is '''not''' set to <code>unlimited</code> (a.k.a. [[LONG_MAX]]).
+Both <code>vzctl</code> and the kernel treats a configuration file as vswap one if PHYSPAGES limit is '''not''' set to <code>unlimited</code> (a.k.a. [[LONG_MAX]]). You can also use the following command:
 In addition, vzctl checks if kernel support vswap, and refuses to start a vswap-enabled container on a non vswap capable kernel. The check is presence of <code>/proc/vz/vswap</code> file.