On Tue, 2007-01-16 at 12:40 +0200, Constantine Shulyupin wrote:
> SWAP (key 'p')
>
> The size of swapped out portion of a task's virtual memory image. This
> field is sometimes confusing, here is why:
>
> Logically, you would expect this field really shows whether your
> program is partially swapped out and how much. But the reality shows
> otherwise. Even the "Swap used" field shows 0, you will be surprised
> that SWAP field of each tasks show greater than zero number. So,
> what's wrong?
>
> This comes from the fact that top use this formula:
>
> VIRT = SWAP + RES or equal
> SWAP = VIRT - RES
>
> As explained previously, VIRT includes anything inside task's address
> space, no matter it is in RAM, swapped out or still not loaded from
> disk. While RES represents total RAM consumed by this task. So, SWAP
> here means it represents the total amount of data being swapped out OR
> still not loaded from disk.
I see. I don't think SWAP is exactly VIRT - RES: for example, the
sensors applet has VIRT 94MB, RES 15MB and SHR 8M, but SWAP is listed as
75MB.
For most apps, it looks as if SWAP is indeed = VIRT - RES which, if RES
includes SHR, seems to me to indicate that all the memory mapped to the
task is either resident or swapped: which is consistent with my feel of
the system where when the accumulated VIRT of all the processes about
equals available swap space + dynamic memory then the system breaks.
--
Oded
::..
"Hey Mr. postman look and see, what you have in the bag for me. It could
be a bomb or it could be a letter - it doesn't matter, things can only
get better."
-- 'When the rainbow comes' / Paula Cole
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