2013. 6. 22. 오전 9:27에 "Anton Vorontsov" <anton@xxxxxxxxxx>님이 작성:
>
> On Sat, Jun 22, 2013 at 01:44:14AM +0900, Minchan Kim wrote:
> [...]
> > 3. The reclaimed could be greater than scanned in vmpressure_evnet
> > by several reasons. Totally, It could trigger wrong event.
>
> Yup, and in that case the best we can do is just ignore the event (i.e.
> not pass it to the userland): thing is, based on the fact that
> 'reclaimed > scanned' we can't actually conclude anything about the
> pressure: it might be still high, or we actually freed enough.
>
> Thanks,
>
> Anton
>
> p.s. I was somewhat sure that someone sent a patch to ignore 'reclaimed >
> scanned' situation, but I cannot find it in my mailbox. Maybe I was
> dreaming about it? :)
I have suggested it as follows and Minchan reviewed it.
I'll send it again after applying Minchan's opinion.
Thanks,
Hyunhee Kim.
=========================================
On Wed, Jun 05, 2013 at 05:31:30PM +0900, Hyunhee Kim wrote:
> Hi, Anton,
>
Sorry, I'm not Anton but I involved a little bit when this feature was
developed so may I answer your qeustion?
> When calculating pressure level in vmpressure_calc_level, I observed that "reclaimed" becomes larger than "scanned".
> In this case, since these values are "unsigned long", pressure
returns wrong value and critical event is triggered even on low state.
> Do you think that it is possible?
True, we have a few reasons.
Culprits I can think easily are THP page reclaiming or bails out reclaiming
by fatal signal in shrink_inactive_list.
I guess you don't enable THP so I think culprit is latter.
> If so, in this case, should we make "reclaimed" equal to "scanned"?
> When I tested as below, it could trigger reasonable events.
>
> =============================
> +static enum vmpressure_levels vmpressure_calc_level(unsigned long scanned,
> + unsigned long reclaimed)
> +{
> + unsigned long scale = scanned + reclaimed;
> + unsigned long pressure;
> + if (reclaimed > scanned)
> + reclaimed = scanned;
Could we simply return VMPRESSURE_LOW?
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