Messages in this thread | ![/](/images/icornerl.gif) | | Date | Tue, 23 Nov 2010 12:35:35 -0800 | From | Andrew Morton <> | Subject | Re: [RFC 1/2] deactive invalidated pages |
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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*.
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.
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.
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