Re: Swapping on Solaris

This page may be of use:

http://www.serverworldmagazine.com/monthly/2003/02/solaris.shtml

 From personal experience, for god's sake don't think Solaris' VM/swap
implementation is easy - it's damn good, but it ain't easy!

Matt

Kevin Schroeder wrote:

> I think it's probably just reserving them.  I can't think of anything
> else. Also, when I run swap activity with sar I don't see any
> activity, which also points to reserved swap space, not used swap space.
>
> swap -s reports
>
> total: 358336k bytes allocated + 181144k reserved = 539480k used,
> 2988840k available
>
> Kevin
>
> ----- Original Message ----- From: "Alan Stange" <stange@rentec.com>
> To: "Kevin Schroeder" <kschroeder@mirageworks.com>
> Cc: <pgsql-performance@postgresql.org>
> Sent: Wednesday, January 19, 2005 11:04 AM
> Subject: Re: [PERFORM] Swapping on Solaris
>
>
>> Kevin Schroeder wrote:
>>
>>> I may be asking the question the wrong way, but when I start up
>>> PostgreSQL swap is what gets used the most of.  I've got 1282MB free
>>> RAM right now and and 515MB swap in use.  Granted, swap file usage
>>> probably wouldn't be zero, but I would guess that it should be a lot
>>> lower so something must be keeping PostgreSQL from using the free
>>> RAM that my system is reporting.  For example, one of my postgres
>>> processes is 201M in size but on 72M is resident in RAM.  That extra
>>> 130M is available in RAM, according to top, but postgres isn't using
>>> it.
>>
>>
>> The test you're doing doesn't measure what you think you're measuring.
>>
>> First, what else is running on the machine?    Note that some shared
>> memory allocations do reserve backing pages in swap, even though the
>> pages aren't currently in use.  Perhaps this is what you're
>> measuring?  "swap -s" has better numbers than top.
>>
>> You'd be better by trying a reboot then starting pgsql and seeing
>> what memory is used.
>>
>> Just because you start a process and see the swap number increase
>> doesn't mean that the new process is in swap.  It means some
>> anonymous pages had to be evicted to swap to make room for the new
>> process or some pages had to be reserved in swap for future use.
>> Typically a new process won't be paged out unless something else is
>> causing enormous memory pressure...
>>
>> -- Alan
>>
>>
>>
>
>
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