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pmap fragmentation
If you look at the pmap(1) output for something like firefox on amd64 you see:
0000000000400000 36K read/exec /usr/pkg/lib/xulrunner/xulrunner-bin
0000000000609000 4K read/write [ anon ]
00007F7FC0400000 64K read/write [ anon ]
00007F7FC0410000 960K read/write [ anon ]
00007F7FC0500000 64K read/write [ anon ]
00007F7FC0510000 960K read/write [ anon ]
00007F7FC0600000 64K read/write [ anon ]
00007F7FC0610000 960K read/write [ anon ]
...
About 1000 on the 1300 lines are read/write anon (presumably mmap()
by the malloc code?) and they are in large blocks of adjacent entries.
Surely it would be better to merge these entries (or rather, create
them by extending the previous one)?
There has to be code to split entries during unmap - as it is valid
to unmap the middle of a mapped area. So ansty effects are unlikely.
David
--
David Laight: david%l8s.co.uk@localhost
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