Re: [RFC 1/3] /dev/low_mem_notify

On Wed, Jan 18, 2012 at 11:41 AM,  [off-list ref] wrote:

quoted

-----Original Message-----
From: penberg@gmail.com [mailto:penberg@gmail.com] On Behalf Of ext
Pekka Enberg
Sent: 18 January, 2012 11:16

...

quoted

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Would be possible to not use percents for thesholds? Accounting in pages

even

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not so difficult to user-space.

How does that work with memory hotplug?

Not worse than %%. For example you had 10% free memory threshold for 512 MB
RAM meaning 51.2 MB in absolute number.  Then hotplug turned off 256 MB, you
for sure must update threshold for %% because these 10% for 25.6 MB most
likely will be not suitable for different operating mode.
Using pages makes calculations must simpler.

Right. Does threshold in percentages make any sense then? Is it enough to use
number of free pages?

On Wed, Jan 18, 2012 at 11:06 AM,  [off-list ref] wrote:

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Also, looking on vmnotify_match I understand that events propagated to
user-space only in case threshold trigger change state from 0 to 1 but not
back, 1-> 0 is very useful event as well

(*)

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Would be possible to use for threshold pointed value(s) e.g. according to
enum zone_state_item, because kinds of memory to track could be

different?

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E.g. to tracking paging activity NR_ACTIVE_ANON and NR_ACTIVE_FILE

could be

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interesting, not only free.

I don't think there's anything in the ABI that would prevent that.

If this statement also related my question (*)  I have to point need to track
attributes history, otherwise user-space will be constantly kicked with
updates.

Well sure, I think it makes sense to support state change to both directions.

When I see code because from emails it is quite difficult to understand.  For
short-term I need to focus on integration "memnotify" version internally
which is kind of work for me already and provides all required interfaces n9
needs.

Sure. I'm only talking about mainline here.

Btw, when API starts to work with pointed thresholds logically it is not

Definitely, it's about generic VM event notification now.

			Pekka

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