Messages in this thread | | | Date | Thu, 11 Mar 2004 23:43:31 +0000 (GMT) | From | Hugh Dickins <> | Subject | Re: anon_vma RFC2 |
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On Thu, 11 Mar 2004, Rik van Riel wrote: > On Thu, 11 Mar 2004, Hugh Dickins wrote: > > > length of your essay on vma merging, it strikes me that you've taken > > a wrong direction in switching from my anon mm to your anon vma. > > > > Go by vmas and you have tiresome problems as they are split and merged, > > very commonly. Plus you have the overhead of new data structure per vma. > > There's of course a blindingly simple alternative. > > Add every anonymous page to an "anon_memory" inode. Then > everything is in effect file backed. Using the same page > refcounting we already do, holes get shot into that "file".
Okay, Rik, the two extremes belong to you: one anon memory object in total (above), and one per page (your original rmap); whereas Andrea is betting on one per vma, and I go for one per mm. Each way has its merits, I'm sure - and you've placed two bets!
> The swap cache code provides a filesystem like mapping > from the anon_memory "files" to the on-disk stuff, or the > anon_memory file pages are resident in memory.
For 2.7 something like that may well be reasonable. But let's beware the fancy bloat of extra levels.
> As a side effect, it also makes it possible to get rid > of the swapoff code, simply move the anon_memory file > pages from disk into memory...
Wonderful if that code could disappear: but I somehow doubt it'll fall out quite so easily - swapoff is inevitably backwards from sanity, isn't it?
Hugh
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