Re: Swapping on Solaris
От | Kevin Schroeder |
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Тема | Re: Swapping on Solaris |
Дата | |
Msg-id | 019701c4fe49$8c72d4a0$0200a8c0@WORKSTATION обсуждение исходный текст |
Ответ на | Swapping on Solaris ("Kevin Schroeder" <kschroeder@mirageworks.com>) |
Ответы |
Re: Swapping on Solaris
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Список | pgsql-performance |
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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