Messages in this thread |  | | Date | Sat, 3 Feb 2007 10:16:28 +0000 | From | Christoph Hellwig <> | Subject | Re: [RFC] Tracking mlocked pages and moving them off the LRU |
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On Fri, Feb 02, 2007 at 10:20:12PM -0800, Christoph Lameter wrote: > This is a new variation on the earlier RFC for tracking mlocked pages. > We now mark a mlocked page with a bit in the page flags and remove > them from the LRU. Pages get moved back when no vma that references > the page has VM_LOCKED set anymore. > > This means that vmscan no longer uselessly cycles over large amounts > of mlocked memory should someone attempt to mlock large amounts of > memory (may even result in a livelock on large systems). > > Synchronization is build around state changes of the PageMlocked bit. > The NR_MLOCK counter is incremented and decremented based on > state transitions of PageMlocked. So the count is accurate. > > There is still some unfinished business: > > 1. We use the 21st page flag and we only have 20 on 32 bit NUMA platforms. > > 2. Since mlocked pages are now off the LRU page migration will no longer > move them. > > 3. Use NR_MLOCK to tune various VM behaviors so that the VM does not > longer fall due to too many mlocked pages in certain areas.
This patch seems to not handle the cases where more than one process mlocks a page and you really need a pincount in the page to not release it before all processes have munlock it or died. I did a similar patch a while ago and tried to handle it by overloading the lru lists pointers with a pincount, but at some point I gave up because I couldn't get that part right.
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