Messages in this thread |  | | Date | Fri, 09 May 2003 10:39:46 -0700 | From | Ulrich Drepper <> | Subject | Re: hammer: MAP_32BIT |
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Andi Kleen wrote:
> That's just an inadequate data structure. It does an linear search of the > VMAs and you probably have a lot of them. Before you add kludges like this > better fix the data structure for fast free space lookup.
If you mean the code in arch_get_unmapped_area(), yes, this needs fixing. In fact, Ingo has already a patch which brings back the performance of thread creation to what we had back in September/October.
> In some vendor kernels it's already in /proc/pid/mapped_base, but that is > quite costly to change. That would probably give you the best of both, Just > set it to a low value for the thread stacks and then reset it to the default. > > I guess that would be the better solution for your stacks.
Are you sure this is the best solution? It means the mmap regions for restricted 31/32 bit addresses and that for the normal, unrestricted mapping is continuous. This removes a lot of freedom in deciding where the unrestricted mappings are best located and it would make programs using threads have a very different memory layout. Not that it should make any difference; but I can here /them/ already scream that this breaks applications.
My kernel-uninformed opinion would be to keep the settings separate.
Oh, and please rename MAP_32BIT to MAP_31BIT. This will save nerves on all sides.
- -- - --------------. ,-. 444 Castro Street Ulrich Drepper \ ,-----------------' \ Mountain View, CA 94041 USA Red Hat `--' drepper at redhat.com `--------------------------- -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux)
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