Messages in this thread | | | Date | Wed, 3 Sep 2003 15:38:10 +0100 | From | Jamie Lokier <> | Subject | Re: [PATCH] Alternate futex non-page-pinning and COW fix |
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Hugh Dickins wrote: > Will it be worth the code added to handle it? I wonder the same of > non-linear (sys_mremap and sys_remap_file_pages, familiar troublemakers). > But all credit for handling them, good to reduce "undefined behaviour"s.
I dismissed remap_file_pages the same as you at first, but since Andrew mentioned it, I think it's a fair point. As long as it's there, programmers should get the natural behaviour from it.
Databases (tdb I think) use futexes in database files, and remap_file_pages is used to look at different views of database files, and for huge files, so... It seems reasonable. That's quite an easy bit of code anyway. The futexes nicely stay persistent even when their particular offset into the file isn't mapped.
mremap() is used for moving anonymous data structures around mainly. Applications don't really need to depend on the futexes moving in that, but it is what the current implementation does so they might exist by now. The code for this is less defensible as it is more complicated.
-- Jamie
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