[mythtv-users] Playback problem -- random short pauses

Steven Adeff adeffs.mythtv at gmail.com
Wed Apr 20 16:34:19 UTC 2011

On Sun, Apr 17, 2011 at 1:21 PM, Mark Lord <mythtv at rtr.ca> wrote:
> On 11-04-17 01:06 PM, Mark Lord wrote:
>> On 11-04-17 11:57 AM, Steven Adeff wrote:
>>> what happens when the systems use all their physical RAM?
>> What happens when the systems use all their physical SWAP?
>> Same thing, same reason.
>> If something is leaking memory badly enough for the system
>> to require swap space, then it will leak badly enough to
>> consume the swap space as well (most people don't configure
>> very much swap).
>> If you've already got swap, then keep it.  It's harmless.
>> Just think about.. "conventional wisdom" says to always configure
>> as much swap as you have RAM.  Which effectively doubles the
>> amount of RAM.
>> Personally, I prefer to REALLY double the amount of RAM,
>> and then not bother with swap.
> A little more background might help people to make informed decisions
> about this topic.
> "Swap" space is used ONLY to temporarily hold memory that has
> been *modified* by a running process, and only then when the
> system is low on unused physical RAM.
> "Swap" space is not used to hold code and/or unmodified data
> from an application --> Linux can re-read that stuff from the
> original program file, so there's no need to write it out
> to swap space when freeing RAM.
> When the system is low on RAM, with or without swap space,
> Linux can free RAM by discarding unmodified pages from memory.
> Things like idle programs, or idle parts of programs, large
> data tables, unmodified file contents etc..
> When things like that get discarded, and then are later needed again,
> Linux will just re-read them from the file where they originally
> were read from.  No big deal, and no need/involvement for swap space.
> Swap usually only comes into the picture when a running process
> has accumulated a ton of modified memory -- run time variables
> and data structures.  Nearly always this stuff comes from "malloc()".
> When the system needs more RAM for something, and discarding
> unmodified pages is insufficient, then it will try to write out
> modified memory to swap space so that those pages can then be
> temporarily freed up for other uses.  This is and should be rare.

thanks for the more technical explanation. I realize at a high level
what swap does, and in concept what a system without swap does, but
this information is much more detailed, thank you.

I've disabled the swap space and I will see if it makes for an
improvement, or a detriment to the system performance.

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