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− | + | System resource control parameters have certain interdependencies. Constraints on the parameter settings are listed below. Indexes <code>bar 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 | |
− | + | is invalid if these constraints are not satisfied. The best way to ensure the | |
− | Configuration of resource control parameters for a | + | validity of the configuration is to use [http://openvz.org/documentation/man/vzcfgvalidate.8 vzcfgvalidate(8)] utility. |
− | is invalid if these constraints are not satisfied. | ||
− | validity of the configuration is to use | ||
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; |
− | + | * Virtual Environment 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 applications | + | This constraint is important for reliable work of applications in the |
− | + | Virtual Environment. | |
− | If it is not satisfied, applications will start to fail | + | If it is not satisfied, applications will start to fail at the middle of |
− | operations instead of failing | + | operations instead of failing at the moment of spawning more processes, |
− | and the application | + | and the application abilities 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 | + | Increasing the left side will increase performance to certain extent. |
− | == UDP socket buffers should be | + | == UDP socket buffers should be big 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. | |
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 | + | == Number of file 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 | + | Note that each process after <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 | |
− | during <code>execve(2)</code> | + | during <code>execve(2)</code> call with diagnostics not clear |
− | + | for 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 | |
− | file operation refusals | + | file operation refusals not expected by applications. |
== 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. | ||
− | + | [[Category:UBC]] | |
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[[Category:Troubleshooting]] | [[Category:Troubleshooting]] |