Re: [PATCH] mem notifications v3

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

Hi Marcelo-san

> > > +			pages_reserve += zone->lowmem_reserve[MAX_NR_ZONES-1];
> > 
> > Hmm...
> > may be, don't works well.
> > 
> > MAX_NR_ZONES determined at compile time and determined by distribution vendor.
> > but real highest zone is determined by box total memory.
> 
> That is OK because the calculation of lowmem reserves will take into account 
> all zones (mm/page_alloc.c::setup_per_zone_lowmem_reserve).

really?
sorry, I will check again.


> But it might be better to use the precalculated totalreserve_pages instead.

Hmm...
unfortunately, accumulate of all zone memory is incompatible to NUMA awareness.
please think again.


> > > +		if (pages_free < (pages_high+pages_reserve)*2) 
> > > +			val = POLLIN;
> > 
> > why do you choice fomula of (pages_high+pages_reserve)*2 ?
> 
> Just to make sure its not sending a spurious notification in the case the system
> has enough free memory already.

Can I think "*2" is your experimental rule? 
if so, I agree your experience.


> > > -static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
> > > +static bool shrink_active_list(unsigned long nr_pages, struct zone *zone,
> > >  				struct scan_control *sc, int priority)
> > 
> > unnecessary type change.
> > if directly call mem_notify_userspace() in shrink_active_list, works well too.
> > because notify rate control can implement by mem_notify_userspace() and mem_notify_poll().
> 
> Yes, and doing that should also guarantee that the notification is sent
> before swapout is performed (right now it sends the notification after
> shrink_inactive_list(), which is performing swapout).

Agreed.


- kosaki

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