Messages in this thread | | | Date | Wed, 9 Apr 2008 08:08:54 +0200 | From | Andi Kleen <> | Subject | Re: bootmem allocator |
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On Tue, Apr 08, 2008 at 11:00:28PM -0700, Mike Travis wrote: > Ingo Molnar wrote: > > * Andi Kleen <andi@firstfloor.org> wrote: > > > >>> hm, bootmem allocator is supposed to clear memory. We have a couple > >>> of places that rely on that. > >> I was actually considering to change that for the GB pages hugetlbfs > >> patchkit, because memset for 1G is a little slow and not needed (will > >> be cleared later anyways) and it might be a problem for very large > >> systems with a lot of such pages at boot. > > > > changing the default behavior of bootmem alloc to be non-clearing is a > > really bad idea that will only cause unrobustness. The proper approach > > is to add an _opt-in_ API that does not clear memory > > (bootmem_alloc_dontclear() or whatever), available to callers that know > > it for sure that they dont need the clearing. > > Yes, changing the default of bootmem_alloc is a bad idea. I just changed > a bunch of static arrays to bootmem alloc's and it was pointed out early > that not only does bootmem_alloc clear memory, but also panics if it's not > available.
There are more and more bootmem calls that don't want the panic actually. That is why _nopanic was invented (and gets more and more variants) At some point the default could be even switched.
I think the right way would be to survey the callers (there are not that many) and then come up with a sane single API that caters to the majority of them by default and passes flags for the special cases.
-Andi
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