Re: [PATCH] VM: Implements the swap-out page-clustering technique

[Li Yu]

Li Yu åé:
> hamidreza jahanjou åé:
> > 2008/9/8, Li Yu <raise.sail@xxxxxxxxx>:
> >   
> > > And the linear searching for whole address space of a vma is not good
> > > idea too, really.
> > >
> > >     
> > > > +	    if (!page_allowed_in_cluster(cursor_page, ci))
> > > > +		continue;
> > > >
> > > >       
> >
> > Thank you for the review and comments. You are right in that searching
> > the whole process address space is not a good idea. The idea is to
> > make the scan range flexible, thus normally, assuming that the code
> > has been well-tuned, only a very limited number of VMA's are scanned.
> >
> > In general, i think that the cluster size and the scan range should be
> > tuned depending on the backing storage characteristics and the
> > low-on-memory severity. Like any VM code, this one needs tuning.
> >
> > BTW, the code could be implemented much more elegantly if the VMA's
> > were connected using a doubly-linked list. I wonder if there are
> > enought other codes with the same situation to justify making it
> > doubly-linked.
> >   
>
> You are welcome!
>
> I think that scanning one vma each task is enough.
>
> The goal of swapoutclustering is to reduce disk heads movement while 
> swapping in, it is based on space/time locality. I think that 
> different vmas implied different using pattern, which also means they 
> have different in  program locality. Therefore, I think scanning multi 
> vmas per task is not a good idea.
>
> Maybe, we need a page cache searching like for anonymous mapping 
> instead of *linear*  searching in each vma.
>
> I also have an uncompleted implementation for this feature ^_^
>
> Good luck.

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