topas - computational memory 95% : Any Impact? Post: 302493000

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Operating Systems AIX topas - computational memory 95% : Any Impact? Post 302493000 by bakunin on Wednesday 2nd of February 2011 05:07:57 AM

02-02-2011

Registered User

Quote:

Originally Posted by zxmaus

well let me disagree here ... computational memory above 85% is never a good idea

Depending on the exact circumstances this is true in most cases, of course. I was a bit too general in my answer.

@panchpan:

Your vmstat output shows several things. First let's look at the memory situation: The "avm" and "fre" columns are displayed in pages of 4k each. You roughly have 5.5 mio pages available ( 5.5 mio x 4k ~ 22GB ) and of these are ~25k pages (~100MB) not used by the system at all. This might be a bit on the light side as a reserve and - as zxmaus has pointed out - you should watch and monitor the system closely to proactively find out probably bottlenecks. Even if you don't have one you might be close to getting one, as zxmaus has already suggested.

On the other hand your "pi" and "po" columns (page in / page out) are constantly zero, which means there is no paging going on yet. Your "vmstat -s" output shows some paging activity, which should be investigated. Issue the same command over the next days once a day and compare the numbers in it. If they remain constant there is nothing to worry, if they increase then paging is happening somewhere and it will be worth it to find out what causes it.

You might also want to issue "vmstat -v" and watch if there are I/O-buffers lacking. (there are also several threads here discussing exactly this)

The CPU part of your vmstat output shows relatively high idle values (id). "us", "sy", "id" and "wa" are percentage values, depicting the time the CPU(s) spend working on user code (basically programs), system code, idling and waiting (for I/O). High waiting numbers mean there are I/O-bottlenecks, because there would be programs ready to do something, which they cannot do because they cannot read their data. There is no such thing in your output, which is a sign of healthiness in this regard.

Notice the "ec" column: this is also a percentage value and signifies the "entitled [CPU] capacity consumed". Your system is allowed to use 2 CPUs and of these about 25% on average (0.5 CPUs) is used. If this value is constantly below 50% you might want to reduce the entitlement to 1 CPU, if it constantly nears 100% you might want to add a CPU to the LPAR configuration. But before suggesting something in this direction first monitor closely over a longer time. There is no sense in doing performance optimization from a single seconds-long snapshot.

I hope these tips help.

bakunin

bakunin

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LEARN ABOUT OPENSOLARIS

vmstat

vmstat(1M)						  System Administration Commands						vmstat(1M)

NAME

       vmstat - report virtual memory statistics

SYNOPSIS

       vmstat [-cipqsS] [disks] [interval [count]]

DESCRIPTION

       vmstat reports virtual memory statistics regarding kernel thread, virtual memory, disk, trap, and CPU activity.

       On MP (multi-processor) systems, vmstat averages the number of CPUs into the output. For per-processor statistics, see mpstat(1M).

       vmstat only supports statistics for certain devices. For more general system statistics, use sar(1), iostat(1M), or sar(1M).

       Without options, vmstat displays a one-line summary of the virtual memory activity since the system was booted.

       During  execution  of the kernel status command, the state of the system can change. If relevant, a state change message is included in the
       vmstat output, in one of the following forms:

	 <<device added: sd0>>
	 <<device removed: sd0>>
	 <<processors added: 1, 3>>
	 <<processors removed: 1, 3>>

       See  for device naming conventions for disks.

OPTIONS

       The following options are supported:

       -c    Report cache flushing statistics. This option is obsolete, and no longer meaningful. This option might be removed in a future version
	     of Solaris.

       -i    Report the number of interrupts per device. count and interval does not apply to the -i option.

       -p    Report paging activity in details. This option will display the following, respectively:

	     epi    Executable page-ins.

	     epo    Executable page-outs.

	     epf    Executable page-frees.

	     api    Anonymous page-ins.

	     apo    Anonymous page-outs.

	     apf    Anonymous page-frees.

	     fpi    File system page-ins.

	     fpo    File system page-outs.

	     fpf    File system page-frees.

	     When executed in a zone and if the pools facility is active, all of the above only report actitivity on the processors in the proces-
	     sor set of the zone's pool.

       -q    Suppress messages related to state changes.

       -s    Display the total number of various system events since boot. count and interval does not apply to the -s option.

       -S    Report on swapping rather than paging activity. This option will change two fields in vmstat's ``paging'' display:  rather  than  the
	     ``re'' and ``mf'' fields, vmstat will report ``si'' (swap-ins) and ``so'' (swap-outs).

OPERANDS

       The following operands are supported:

       count	   Specifies the number of times that the statistics are repeated. count does not apply to the -i and -s options.

       disks	   Specifies which disks are to be given priority in the output (only four disks fit on a line). Common disk names are id, sd, xd,
		   or xy, followed by a number (for example, sd2, xd0, and so forth).

       interval    Specifies the last number of seconds over which vmstat summarizes activity. This number of seconds  repeats	forever.  interval
		   does not apply to the -i and -s options.

EXAMPLES

       Example 1 Using vmstat

       The following command displays a summary of what the system is doing every five seconds.

	 example% vmstat 5

	 kthr	memory		page		 disk	   faults	 cpu
	 r b w swap  free re mf pi p fr de sr s0 s1 s2 s3  in  sy  cs us sy id
	 0 0 0 11456 4120 1  41 19 1  3  0  2  0  4  0	0  48 112 130  4 14 82
	 0 0 1 10132 4280 0   4 44 0  0  0  0  0 23  0	0 211 230 144  3 35 62
	 0 0 1 10132 4616 0   0 20 0  0  0  0  0 19  0	0 150 172 146  3 33 64
	 0 0 1 10132 5292 0   0  9 0  0  0  0  0 21  0	0 165 105 130  1 21 78
	 1 1 1 10132 5496 0   0  5 0  0  0  0  0 23  0	0 183  92 134  1 20 79
	 1 0 1 10132 5564 0   0 25 0  0  0  0  0 18  0	0 131 231 116  4 34 62
	 1 0 1 10124 5412 0   0 37 0  0  0  0  0 22  0	0 166 179 118  1 33 67
	 1 0 1 10124 5236 0   0 24 0  0  0  0  0 14  0	0 109 243 113  4 56 39
	 ^C

	 example%

       The fields of vmstat's display are

       kthr	 Report the number of kernel threads in each of the three following states:

		 r    the number of kernel threads in run queue

		 b    the number of blocked kernel threads that are waiting for resources I/O, paging, and so forth

		 w    the number of swapped out lightweight processes (LWPs) that are waiting for processing resources to finish.

       memory	 Report on usage of virtual and real memory.

		 swap	 available swap space (Kbytes)

		 free	 size of the free list (Kbytes)

       page	 Report  information  about page faults and paging activity. The information on each of the following activities is given in units
		 per second.

		 re    page reclaims -- but see the -S option for how this field is modified.

		 mf    minor faults -- but see the -S option for how this field is modified.

		 pi    kilobytes paged in

		 po    kilobytes paged out

		 fr    kilobytes freed

		 de    anticipated short-term memory shortfall (Kbytes)

		 sr    pages scanned by clock algorithm

		 When executed in a zone and if the pools facility is active, all of the above (except for "de") only report activity on the  pro-
		 cessors in the processor set of the zone's pool.

       disk	 Report  the  number of disk operations per second. There are slots for up to four disks, labeled with a single letter and number.
		 The letter indicates the type of disk (s = SCSI, i = IPI, and so forth); the number is the logical unit number.

       faults	 Report the trap/interrupt rates (per second).

		 in    interrupts

		 sy    system calls

		 cs    CPU context switches

		 When executed in a zone and if the pools facility is active, all of the above only report actitivity on  the  processors  in  the
		 processor set of the zone's pool.

       cpu	 Give a breakdown of percentage usage of CPU time. On MP systems, this is an average across all processors.

		 us    user time

		 sy    system time

		 id    idle time

		 When  executed  in  a	zone and if the pools facility is active, all of the above only report actitivity on the processors in the
		 processor set of the zone's pool.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |See below.		   |
       +-----------------------------+-----------------------------+

       Invocation is evolving. Human readable output is unstable.

SEE ALSO

       sar(1), iostat(1M), mpstat(1M), sar(1M), attributes(5)

NOTES

       The sum of CPU utilization might vary slightly from 100 because of rounding errors in the production of a percentage figure.

       The -c option (Report cache flushing statistics) is not supported in this release.

SunOS 5.11							    20 Dec 2004 							vmstat(1M)