Messages in this thread |  | | Date | Fri, 01 Nov 2013 16:38:35 -0400 | From | KOSAKI Motohiro <> | Subject | Re: [PATCH] mm: cache largest vma |
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(11/1/13 4:17 PM), Davidlohr Bueso wrote: > While caching the last used vma already does a nice job avoiding > having to iterate the rbtree in find_vma, we can improve. After > studying the hit rate on a load of workloads and environments, > it was seen that it was around 45-50% - constant for a standard > desktop system (gnome3 + evolution + firefox + a few xterms), > and multiple java related workloads (including Hadoop/terasort), > and aim7, which indicates it's better than the 35% value documented > in the code. > > By also caching the largest vma, that is, the one that contains > most addresses, there is a steady 10-15% hit rate gain, putting > it above the 60% region. This improvement comes at a very low > overhead for a miss. Furthermore, systems with !CONFIG_MMU keep > the current logic.
I'm slightly surprised this cache makes 15% hit. Which application get a benefit? You listed a lot of applications, but I'm not sure which is highly depending on largest vma.
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