Messages in this thread | | | From | Andy Lutomirski <> | Date | Mon, 26 Nov 2012 12:12:16 -0800 | Subject | mmap_sem contention issues |
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I'm having serious latency problems due to mmap_sem contention. I have a real-time thread that has (soft) page faults on locked pages, and it blocks for multiple milliseconds on (call_rwsem_down_read_failed do_page_fault page_fault). Can this be fixed?
Some ideas:
1. Drop mmap_sem during the filesystem part of mmap and munmap. (MAP_POPULATE in particular is a disaster -- using it will easily increase latency from a few milliseconds to a respectable fraction of a second.)
2. Come up with some way to lock specific vm_area_structs for read access without taking mmap_sem at all. This looks unpleasant with the current rbtree structure -- something like a radix tree might work much better if the nodes were to contain their own locks.
--Andy
-- Andy Lutomirski AMA Capital Management, LLC
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