Difference between revisions of "UBC consistency check"

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System resource control parameters have certain interdependencies. Constraints on the parameter settings are listed below. Indexes <code>bar</code> and <code>lim</code> in the formulae below mean the barrier and the limit of the parameters, respectively.
 
System resource control parameters have certain interdependencies. Constraints on the parameter settings are listed below. Indexes <code>bar</code> and <code>lim</code> in the formulae below mean the barrier and the limit of the parameters, respectively.
  
Configuration of resource control parameters for a Virtual Environment
+
Configuration of resource control parameters for a container
is invalid if these constraints are not satisfied. The best way to ensure the
+
is invalid if these constraints are not satisfied. '''The best way to ensure the
validity of the configuration is to use {{man|vzcfgvalidate|8}} utility.
+
validity of the configuration is to use the {{man|vzcfgvalidate|8}} utility.'''
  
 
All the interdependencies discussed below and their importance are summarized in [[UBC interdependencies table]].
 
All the interdependencies discussed below and their importance are summarized in [[UBC interdependencies table]].
  
 
The configured limits can be checked through
 
The configured limits can be checked through
* <code>/proc/user beancounters</code> interface;
+
* /[[proc/user_beancounters]] interface;
* Virtual Environment configuration files in <code>/etc/vz/conf/</code> directory.
+
* [[BC proc entries|/proc/bc/]] interface;
 +
* {{Man|vzubc|8}} utility;
 +
* container configuration files in <code>/etc/vz/conf/</code> directory;
  
  
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(<code>avnumproc</code> here stands for the expected average number of processes).
 
(<code>avnumproc</code> here stands for the expected average number of processes).
  
This constraint is important for reliable work of applications in the
+
This constraint is important for applications to work reliably in the
Virtual Environment.
+
container.
If it is not satisfied, applications will start to fail at the middle of
+
If it is not satisfied, applications will start to fail in the middle of
operations instead of failing at the moment of spawning more processes,
+
operations instead of failing while spawning more processes
and the application abilities to handle resource shortage will be very
+
and the application's ability to handle resource shortage will be very
 
limited.
 
limited.
  
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Selecting the left side equal to the right side in the inequalities
 
Selecting the left side equal to the right side in the inequalities
 
above ensures minimal performance of network communications.
 
above ensures minimal performance of network communications.
Increasing the left side will increase performance to certain extent.
+
Increasing the left side will increase performance to a certain extent.
  
== UDP socket buffers should be big enough if the system is not tight on memory ==
+
== UDP socket buffers should be large enough if the system is not tight on memory ==
 
<math>dgramrcvbuf_{bar} \ge 129KB</math>
 
<math>dgramrcvbuf_{bar} \ge 129KB</math>
  
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These constraints are desired, but not essential.
 
These constraints are desired, but not essential.
Big enough buffers for UDP sockets improve reliability of datagram delivery.
+
Large enough buffers for UDP sockets improve reliability of datagram delivery.
 
However, note that if the UDP traffic is so bursty that it needs larger
 
However, note that if the UDP traffic is so bursty that it needs larger
 
buffers, the datagrams will likely be lost not because of resource control
 
buffers, the datagrams will likely be lost not because of resource control
 
limits, but because of other memory and performance limitations.
 
limits, but because of other memory and performance limitations.
  
== Number of file limit should be adequate for the expected number of processes ==
+
== Number of files limit should be adequate for the expected number of processes ==
 
<math>numfile \ge avnumproc \cdot 32</math>
 
<math>numfile \ge avnumproc \cdot 32</math>
  
Note that each process after <code>execve(2)</code> system call
+
Note that each process after a <code>execve(2)</code> system call
 
requires a file for each loaded shared library.
 
requires a file for each loaded shared library.
Too low <code>numfile</code> limit will increase the chances of failures
+
A too low <code>numfile</code> limit will increase the chances of failures
during <code>execve(2)</code> call with diagnostics not clear
+
during <code>execve(2)</code> calls with error messages that are not clear
for the users.
+
to the users.
  
 
== The limit on the total size of <code>dentry</code> and <code>inode</code> structures locked in memory should be adequate for allowed number of files ==
 
== The limit on the total size of <code>dentry</code> and <code>inode</code> structures locked in memory should be adequate for allowed number of files ==
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<math>dcachesize_{bar} \ge numfile \cdot 384\ \rm(bytes)</math>
 
<math>dcachesize_{bar} \ge numfile \cdot 384\ \rm(bytes)</math>
  
Too low <code>dcachesize</code> limit will increase the chances of
+
A too low <code>dcachesize</code> limit will increase the chances of
file operation refusals not expected by applications.
+
file operation refusals resulting in unexpected application failures.  
  
 
== Barrier should be less or equal than limit ==
 
== Barrier should be less or equal than limit ==
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should be maintained for each parameter.
 
should be maintained for each parameter.
 +
 +
== Code ==
 +
See [[User:Grin/openvz checker.pl]] for a contributed code to check the consistency.
  
 
[[Category:Troubleshooting]]
 
[[Category:Troubleshooting]]

Latest revision as of 22:35, 23 November 2014

User Beancounters
Definition
/proc/user_beancounters
/proc/bc/
General information
Units of measurement
VSwap
Parameters description
Primary parameters
numproc, numtcpsock, numothersock, vmguarpages
Secondary parameters
kmemsize, tcpsndbuf, tcprcvbuf, othersockbuf, dgramrcvbuf, oomguarpages, privvmpages
Auxiliary parameters
lockedpages, shmpages, physpages, numfile, numflock, numpty, numsiginfo, dcachesize, numiptent, swappages
Internals
User pages accounting
RSS fractions accounting
On-demand accounting
UBC consistency
Consistency formulae
System-wide configuration
vzubc(8)
Configuration examples
Basic
Derived
Intermediate configurations
Tables
List of parameters
Parameter properties
Consistency
Config examples

System resource control parameters have certain interdependencies. Constraints on the parameter settings are listed below. Indexes bar and lim in the formulae below mean the barrier and the limit of the parameters, respectively.

Configuration of resource control parameters for a container is invalid if these constraints are not satisfied. The best way to ensure the validity of the configuration is to use the vzcfgvalidate(8) utility.

All the interdependencies discussed below and their importance are summarized in UBC interdependencies table.

The configured limits can be checked through


kmemsize should be enough for the expected number of processes[edit]

(avnumproc here stands for the expected average number of processes).

This constraint is important for applications to work reliably in the container. If it is not satisfied, applications will start to fail in the middle of operations instead of failing while spawning more processes and the application's ability to handle resource shortage will be very limited.

Memory allocation limits should not be less than the guarantee[edit]

If this constraint is not satisfied, vmguarpages will not work.

Send buffers should have enough space for all sockets[edit]

These constraints are also important. If they are not satisfied, transmission of data over the sockets may hang in some circumstances.

Other TCP socket buffers should be big enough[edit]

Selecting the left side equal to the right side in the inequalities above ensures minimal performance of network communications. Increasing the left side will increase performance to a certain extent.

UDP socket buffers should be large enough if the system is not tight on memory[edit]

These constraints are desired, but not essential. Large enough buffers for UDP sockets improve reliability of datagram delivery. However, note that if the UDP traffic is so bursty that it needs larger buffers, the datagrams will likely be lost not because of resource control limits, but because of other memory and performance limitations.

Number of files limit should be adequate for the expected number of processes[edit]

Note that each process after a execve(2) system call requires a file for each loaded shared library. A too low numfile limit will increase the chances of failures during execve(2) calls with error messages that are not clear to the users.

The limit on the total size of dentry and inode structures locked in memory should be adequate for allowed number of files[edit]

A too low dcachesize limit will increase the chances of file operation refusals resulting in unexpected application failures.

Barrier should be less or equal than limit[edit]

In addition to the conditions listed above,

should be maintained for each parameter.

Code[edit]

See User:Grin/openvz checker.pl for a contributed code to check the consistency.