Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [RFC PATCH 2/2] arm64: Implement vmalloc based thread_info allocator | Date | Sun, 24 May 2015 19:49:01 +0200 |
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On Monday 25 May 2015 01:02:20 Jungseok Lee wrote: > Fork-routine sometimes fails to get a physically contiguous region for > thread_info on 4KB page system although free memory is enough. That is, > a physically contiguous region, which is currently 16KB, is not available > since system memory is fragmented. > > This patch tries to solve the problem as allocating thread_info memory > from vmalloc space, not 1:1 mapping one. The downside is one additional > page allocation in case of vmalloc. However, vmalloc space is large enough, > around 240GB, under a combination of 39-bit VA and 4KB page. Thus, it is > not a big tradeoff for fork-routine service.
vmalloc has a rather large runtime cost. I'd argue that failing to allocate thread_info structures means something has gone very wrong.
Can you describe the scenario that leads to fragmentation this bad?
Could the stack size be reduced to 8KB perhaps?
Arnd
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