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ioacct interpretation and unit [message #36076]

Tue, 19 May 2009 15:29

Atosboy
Messages: 15
Registered: April 2009

Junior Member

Hi,

We try to analyze the behavior of our system in OpenVZ environnement. In order to see it behavior, we periodically capture the content of /proc/bc/<veid>/ioacct file and try to interpret theses indicators.
We are from of several problems :
+ What represent each counter(read, write, vfs_read, vfs_write, ....)?
+ What is the unit for each counter(Kb, Block, ...)?

Thank for your help,

Pat

NB : For instance, the first snapshot is :
090515_14h48m06 read 1081344
090515_14h48m06 write 684281856
090515_14h48m06 dirty 684572672
090515_14h48m06 cancel 37818368
090515_14h48m06 missed 0
090515_14h48m06 syncs_total 0
090515_14h48m06 fsyncs_total 46
090515_14h48m06 fdatasyncs_total 1
090515_14h48m06 range_syncs_total 0
090515_14h48m06 syncs_active 0
090515_14h48m06 fsyncs_active 0
090515_14h48m06 fdatasyncs_active 0
090515_14h48m06 range_syncs_active 0
090515_14h48m06 vfs_reads 4737583
090515_14h48m06 vfs_read_chars 576083171
090515_14h48m06 vfs_writes 281962
090515_14h48m06 vfs_write_chars 829761534
090515_14h48m06 io_pbs 71

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Re: ioacct interpretation and unit [message #36082 is a reply to message #36076]

Wed, 20 May 2009 11:53

maratrus
Messages: 1495
Registered: August 2007
Location: Moscow

Senior Member

Hi,

to get full information you'd better look through kernel sources Smile

I doubt that all of the output numbers help you very much but I'd like to explain a little bit "dirty" and "write" numbers' meaning.

Writing to disk might be divided into two phases: writing to page and then writing to disk. "dirty" and "write" fields of /proc/bc/$VEID/ioacct output correspond to the former and to the latter phases.
So, if a "dirty" field is continuously growing and "write" field is not (or much slower that "dirty") this means that i/o scheduler doesn't allow this particular VE to write to disk.

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Re: ioacct interpretation and unit [message #36169 is a reply to message #36082]

Tue, 26 May 2009 13:32

Atosboy
Messages: 15
Registered: April 2009

Junior Member

Thank for your help,
We only have analyzed read, write indicators which are documented by Linux Kernel documentation.

Pat

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