on 20/12/2011 16:31 Ganael LAPLANCHE said the following: > On Tue, 20 Dec 2011 15:02:01 +0100 (CET), Ganael LAPLANCHE wrote > >> But there is still something I don't understand : on the Linux >> machine where I ran my test program, the current RLIMIT_DATA >> is set to 0xffffffff/0xffffffff and I can manage to mmap at >> address 0x20000000. If I set the same limit on FreeBSD, I >> won't get the mapping at 0x20000000. So, there *is* a >> difference of behaviour between the two systems, but I don't >> understand why. > > Well, in fact, two things remain not very clear for me : > > - Why are mmap()s performed *after* data segment ? > => It seems they can go within, on GNU/Linux and NetBSD. > > - Why do we have such a default value for datasize (8.2, amd64) : > > $ limits > Resource limits (current): > cputime infinity secs > filesize infinity kB > datasize 33554432 kB > > this is HUGE !
Just a guess - this might be some sort of optimization to keep virtual address range of dynamic allocations untouched by unrelated mmap calls. Not sure if that's so and how useful could that be. svn log / svn annotate of the file may reveal more details. -- Andriy Gapon _______________________________________________ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "freebsd-stable-unsubscr...@freebsd.org"
