Messages in this thread | | | Date | Wed, 25 Apr 2012 15:24:29 -0700 | From | Tejun Heo <> | Subject | Re: [PATCH] mm: percpu: Add PCPU_FC_FIXED to pcpu_fc for setting fixed pcpu_atom_size. |
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Hello, ShouX.
On Wed, Apr 25, 2012 at 04:49:28PM +0800, ShuoX Liu wrote: > From: ShuoX Liu <shuox.liu@intel.com> > > We are enabling Android on Medfield. On i386, if the board has more > physical memory, it means the vmalloc space is small. If the vmalloc > space is big, it means physical memory is small. Dynamic percpu > allocation is based on VM space. On i386, by default, the chunk size > is 4MB. As vmalloc space is <= 128M, percpu allocation often fails.
Can you please provide more details - which kernel/user split was used, how much memory was there and so on? Also, can you please attach boot log and the output of "cat /proc/vmallocinfo"?
> If using PERCPU_FC_PAGE, system can't go to deep sleep states.
Why?
> diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c > index 71f4727..824bc41 100644 > --- a/arch/x86/kernel/setup_percpu.c > +++ b/arch/x86/kernel/setup_percpu.c > @@ -185,9 +185,13 @@ void __init setup_per_cpu_areas(void) > #endif > rc = -EINVAL; > if (pcpu_chosen_fc != PCPU_FC_PAGE) { > - const size_t atom_size = cpu_has_pse ? PMD_SIZE : PAGE_SIZE; > + size_t atom_size; > const size_t dyn_size = PERCPU_MODULE_RESERVE + > PERCPU_DYNAMIC_RESERVE - PERCPU_FIRST_CHUNK_RESERVE; > + if (pcpu_chosen_fc == PCPU_FC_FIXED && pcpu_atom_size) > + atom_size = pcpu_atom_size; > + else > + atom_size = cpu_has_pse ? PMD_SIZE : PAGE_SIZE; > > rc = pcpu_embed_first_chunk(PERCPU_FIRST_CHUNK_RESERVE, > dyn_size, atom_size,
Umm... this is way too hacky. atom_size can't be an arbitrary value and the param is meaningful only to x86 yet defined globally. Also, while atom_size has effect on vmalloc area usage, way more important factor is distance between units. What we probably need to do is tighten the rejection criteria of pcpu_embed_first_chunk() and fix whatever problem FC_PAGE is causing.
Thanks.
-- tejun
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