Messages in this thread | | | Date | Wed, 24 Nov 2010 08:45:20 +0900 | Subject | Re: [RFC 1/2] deactive invalidated pages | From | Minchan Kim <> |
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On Wed, Nov 24, 2010 at 7:10 AM, Mel Gorman <mel@csn.ul.ie> wrote: > On Tue, Nov 23, 2010 at 12:35:35PM -0800, Andrew Morton wrote: >> On Tue, 23 Nov 2010 14:58:56 +0000 >> Mel Gorman <mel@csn.ul.ie> wrote: >> >> > On Tue, Nov 23, 2010 at 09:55:49AM -0500, Ben Gamari wrote: >> > > On Tue, 23 Nov 2010 09:38:59 +0000, Mel Gorman <mel@csn.ul.ie> wrote: >> > > > > If it's mapped pagecache then the user was being a bit silly (or didn't >> > > > > know that some other process had mapped the file). In which case we >> > > > > need to decide what to do - leave the page alone, deactivate it, or >> > > > > half-deactivate it as this patch does. >> > > > > >> > > > >> > > > What are the odds of an fadvise() user having used mincore() in advance >> > > > to determine if the page was in use by another process? I would guess >> > > > "low" so this half-deactivate gives a chance for the page to be promoted >> > > > again as well as a chance for the flusher threads to clean the page if >> > > > it really is to be reclaimed. >> > > > >> > > Do we really want to make the user jump through such hoops as using >> > > mincore() just to get the kernel to handle use-once pages properly? >> > >> > I would think "no" which is why I support half-deactivating pages so they won't >> > have to. >> >> If the page is page_mapped() then we can assume that some other process >> is using it and we leave it alone *altogether*. >> > > Agreed, that makes perfect sense. > >> If the page is dirty or under writeback (and !page_mapped()) then we >> should assume that we should free it asap. The PageReclaim() trick >> might help with that. >> > > Again agreed. > >> I just don't see any argument for moving the page to the head of the >> inactive LRU as a matter of policy. We can park it there because we >> can't think of anythnig else to do with it, but it's the wrong place >> for it. >> > > Is there a better alternative? One thing that springs to mind is that we are > not exactly tracking very well what effect these policy changes have. The > analysis scripts I have do a reasonable job on tracking reclaim activity > (although only as part of the mmtests tarball, I should split them out as > a standalone tool) but not the impact - namely minor and major faults. I > should sort that out so we can put better reclaim analysis in place.
It can help very much. :)
Also, I need time since I am so busy.
> > -- > Mel Gorman > Part-time Phd Student Linux Technology Center > University of Limerick IBM Dublin Software Lab >
-- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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