Messages in this thread | | | Subject | Re: [PATCH 12/30] mm: memory reserve management | From | Peter Zijlstra <> | Date | Tue, 12 Aug 2008 10:12:20 +0200 |
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On Tue, 2008-08-12 at 17:46 +1000, Neil Brown wrote: > On Thursday July 24, a.p.zijlstra@chello.nl wrote: > > Generic reserve management code. > > > > It provides methods to reserve and charge. Upon this, generic alloc/free style > > reserve pools could be build, which could fully replace mempool_t > > functionality. > > More comments on this patch ..... > > > +void *___kmalloc_reserve(size_t size, gfp_t flags, int node, void *ip, > > + struct mem_reserve *res, int *emerg); > > + > > +static inline > > +void *__kmalloc_reserve(size_t size, gfp_t flags, int node, void *ip, > > + struct mem_reserve *res, int *emerg) > > +{ > > + void *obj; > > + > > + obj = __kmalloc_node_track_caller(size, > > + flags | __GFP_NOMEMALLOC | __GFP_NOWARN, node, ip); > > + if (!obj) > > + obj = ___kmalloc_reserve(size, flags, node, ip, res, emerg); > > + > > + return obj; > > +} > > + > > +#define kmalloc_reserve(size, gfp, node, res, emerg) \ > > + __kmalloc_reserve(size, gfp, node, \ > > + __builtin_return_address(0), res, emerg) > > + > ...... > > +/* > > + * alloc wrappers > > + */ > > + > > +void *___kmalloc_reserve(size_t size, gfp_t flags, int node, void *ip, > > + struct mem_reserve *res, int *emerg) > > +{ > > + void *obj; > > + gfp_t gfp; > > + > > + gfp = flags | __GFP_NOMEMALLOC | __GFP_NOWARN; > > + obj = __kmalloc_node_track_caller(size, gfp, node, ip); > > + > > + if (obj || !(gfp_to_alloc_flags(flags) & ALLOC_NO_WATERMARKS)) > > + goto out; > > + > > + if (res && !mem_reserve_kmalloc_charge(res, size)) { > > + if (!(flags & __GFP_WAIT)) > > + goto out; > > + > > + wait_event(res->waitqueue, > > + mem_reserve_kmalloc_charge(res, size)); > > + > > + obj = __kmalloc_node_track_caller(size, gfp, node, ip); > > + if (obj) { > > + mem_reserve_kmalloc_charge(res, -size); > > + goto out; > > + } > > + } > > + > > + obj = __kmalloc_node_track_caller(size, flags, node, ip); > > + WARN_ON(!obj); > > + if (emerg) > > + *emerg |= 1; > > + > > +out: > > + return obj; > > +} > > Two comments to be precise. > > 1/ __kmalloc_reserve attempts a __GFP_NOMEMALLOC allocation, and then > if that fails, ___kmalloc_reserve immediately tries again. > Is that pointless? Should the second one be removed?
Pretty pointless yes, except that it made ___kmalloc_reserve a nicer function to read, and as its an utter slow path I couldn't be arsed to optimize :-)
> 2/ mem_reserve_kmalloc_charge appears to assume that the 'mem_reserve' > has been 'connected' and so is active.
Hmm, that would be __mem_reserve_charge() then, because the callers don't do much.
> While callers probably only set GFP_MEMALLOC in cases where the > mem_reserve is connected, ALLOC_NO_WATERMARKS could get via > PF_MEMALLOC so we could end up calling mem_reserve_kmalloc_charge > when the mem_reserve is not connected.
Right..
> That seems to be 'odd' at least. > It might even be 'wrong' as mem_reserve_connect doesn't add the > usage of the child to the parent - only the ->pages and ->limit. > > What is your position on this? Mine is "still slightly confused".
Uhmm,. good point. Let me ponder this while I go for breakfast ;-)
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