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Originally Posted by
javanoob
Hi Jilliagre
There's an extra "i", my pseudo is jlliagre, not jilliagre...
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q1) Do you mean if ProcessA has made reservation on the virtual swap (ram & disk), another Process B can actually use this reserved space for actual physical paging into RAM and out to swap/disk ?
Unless shared memory enter in the game, no it can't.
Virtual space allocated by a process is for its exclusive use. Note again that virtual memory is not the same as physical memory. No particular space is reserved, that's just an amount of space. The OS is free to map this virtual space to whatever physical backend it likes.
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q2) If i still have free memory (ard 10G reported in memstat's free) but have physical swap being used (ard 3G in swap -l), what does this means then ?
That means the OS stored 3G of seldom used virtual memory to disk, improving overall performance.
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Doing vmstat for 30 minutes, did not see any counters jump for si/so, pi/po, and SR (all 0s) ?
Could i have some kind of spike @ certain timing (using up all the free ram), and cause the physical swap to be use ? < could this be 1 possiblity ?
The si/so counters are unlikely to move under normal circumstances but only during severe RAM shortage.
The pi/po counters move when there pagination occur. Most of that pagination might be unrelated to VM shortage, that might simply be a file being read by some process.
Th sr only move if there is RAM shortage.
A static 3G doesn't cause any activity by itself.
The most important counter to monitor is "sr". As long as it stays equal to 0, there is no RAM shortage.
You might have VM shortage though, and the vmstat column to monitor is then "swap" (available swap space).
Note also that your system might use zones configured with virtual memory capping. In such case you might have swap usage without (global) vm shortage.