Re: [PATCH 4/5] [RFC][HACK] Add LRU_VOLATILE support to the VM

[John Stultz]

On 08/05/2012 08:04 PM, Minchan Kim wrote:
> Hi John,
>
> On Fri, Jul 27, 2012 at 11:57:11PM -0400, John Stultz wrote:
> > In an attempt to push the volatile range managment even
> > deeper into the VM code, this is my first attempt at
> > implementing Minchan's idea of a LRU_VOLATILE list in
> > the mm core.
> >
> > This list sits along side the LRU_ACTIVE_ANON, _INACTIVE_ANON,
> > _ACTIVE_FILE, _INACTIVE_FILE and _UNEVICTABLE lru lists.
> >
> > When a range is marked volatile, the pages in that range
> > are moved to the LRU_VOLATILE list. Since volatile pages
> > can be quickly purged, this list is the first list we
> > shrink when we need to free memory.
> >
> > When a page is marked non-volatile, it is moved from the
> > LRU_VOLATILE list to the appropriate LRU_ACTIVE_ list.
> I think active list promotion is not good.
> It should go to the inactive list and they get a chance to
> activate from inactive to active sooner or later if it is
> really touched.

Ok. Thanks, I'll change it so we move to the inactive list then.


> > This patch introduces the LRU_VOLATILE list, an isvolatile
> > page flag, functions to mark and unmark a single page
> > as volatile, and shrinker functions to purge volatile
> > pages.
> >
> > This is a very raw first pass, and is neither performant
> > or likely bugfree. It works in my trivial testing, but
> > I've not pushed it very hard yet.
> >
> > I wanted to send it out just to get some inital thoughts
> > on the approach and any suggestions should I be going too
> > far in the wrong direction.
> I look at this series and found several nitpicks about implemenataion
> but I think it's not a good stage about concerning it.

Although while I know the design may still need significant change, I'd 
still appreciate nitpicks, as they might help me better understand the 
mm code and any mistakes I'm making.


> Although naming is rather differet with I suggested, I think it's good idea.
> So let's talk about it firstly.
> I will call VOLATILE list as EReclaimale LRU list.
Yea, I didn't want to call it ERECLAIMABLE since for this iteration I 
was limiting the scope just to volatile pages. I'm totally fine renaming 
it as the scope widens.

thanks
-john

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