On Wed, 18 Jan 2012, Minchan Kim wrote:
I didn't look into your code(will do) but as I read description,
still I don't convince we need really some process specific threshold like 99%
I think application can know it by polling /proc/meminfo without this mechanism
if they really want.
I'm not sure if we need arbitrary threshold either. However, we need to
support the following cases:
- We're about to swap
- We're about to run out of memory
- We're about to start OOM killing
and I don't think your patch solves that. One possibility is to implement:
VMNOTIFY_TYPE_ABOUT_TO_SWAP
VMNOTIFY_TYPE_ABOUT_TO_OOM
VMNOTIFY_TYPE_ABOUT_TO_OOM_KILL
and maybe rip out support for arbitrary thresholds. Does that more
reasonable?
As for polling /proc/meminfo, I'd much rather deliver stats as part of
vmnotify_read() because it's easier to extend the ABI rather than adding
new fields to /proc/meminfo.
On Wed, 18 Jan 2012, Minchan Kim wrote:
I would like to notify when system has a trobule with memory pressure without
some process specific threshold. Of course, applicatoin can't expect it.(ie,
application can know system memory pressure by /proc/meminfo but it can't know
when swapout really happens). Kernel low mem notify have to give such notification
to user space, I think.
It should be simple to add support for VMNOTIFY_TYPE_MEM_PRESSURE that
uses your hooks.
Pekka
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