We run into this problem repeatedly... "swap" in Solaris terms refers to
total VM. This is true on most UNIX systems. However, we often
mistakenly refer to pagefile ("swap disk") simply and incorrectly as "swap".
Therefore, the "swap cap" is better thought of as a VM cap. Rcapd
(physical) will keep RSS in check. When exceeded it will page out to
the page file (swap disk). When total VM (RSS+Pagefile+tmpfs) exceeds
the zone.max-swap limit malloc() will fail.
Thus, "swap" is the right term, but its almost universally misused.
Best example is the "swap" column in vmstat output.
Steve Lawrence wrote:
> Swap limits how much of the systems total memory (ram + disk) can be reserved.
> When this limit is hit, allocations, such as malloc, will fail. Physical
> memory limits resident memory. When this limit is hit, the zone will page
> pages in memory to disk swap.
> In general, your example config is only useful if the zone uses a lot of
> physical memory, but does not reserve as much swap. An example is an
> application which maps a large on-disk file into memory. No swap is needed
> for the file, (because the file can be paged back to the a filesystem), but a
> large amount of physical memory may be needed to pull the file into RAM.
> Such applications are rare, so your example config is not often used. Your
> basically right is saying that this config does not make any sense in most
> -Steve L.
> On Fri, Feb 20, 2009 at 08:36:20PM +0100, Alexander Skwar wrote:
>> On Fri, Feb 20, 2009 at 17:50, Asif Iqbal <vad...@gmail.com> wrote:
>>> physical: 1G
>>> [swap: 512M]
>> A question regarding this setting - does that setting really make
>> sense? I suppose he tries to achieve that the zone as a max.
>> uses 1G of real memory and no more than 512M of Swap.
>> But does it really do that?
>> Or is he rather limiting the amount of allocable mem to 512M?
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