Messages in this thread | | | Date | Mon, 27 Apr 2015 15:43:33 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 05/13] mm: meminit: Make __early_pfn_to_nid SMP-safe and introduce meminit_pfn_in_nid |
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On Thu, 23 Apr 2015 11:33:08 +0100 Mel Gorman <mgorman@suse.de> wrote:
> __early_pfn_to_nid() in the generic and arch-specific implementations > use static variables to cache recent lookups. Without the cache > boot times are much higher due to the excessive memblock lookups but > it assumes that memory initialisation is single-threaded. Parallel > initialisation of struct pages will break that assumption so this patch > makes __early_pfn_to_nid() SMP-safe by requiring the caller to cache > recent search information. early_pfn_to_nid() keeps the same interface > but is only safe to use early in boot due to the use of a global static > variable. meminit_pfn_in_nid() is an SMP-safe version that callers must > maintain their own state for.
Seems a bit awkward.
> +struct __meminitdata mminit_pfnnid_cache global_init_state; > + > +/* Only safe to use early in boot when initialisation is single-threaded */ > int __meminit early_pfn_to_nid(unsigned long pfn) > { > int nid; > > - nid = __early_pfn_to_nid(pfn); > + /* The system will behave unpredictably otherwise */ > + BUG_ON(system_state != SYSTEM_BOOTING);
Because of this.
Providing a cache per cpu:
struct __meminitdata mminit_pfnnid_cache global_init_state[NR_CPUS];
would be simpler?
Also, `global_init_state' is a poor name for a kernel-wide symbol.
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