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Date: Tue, 14 Apr 2015 14:31:02 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Ingo Molnar <mingo@...nel.org> Cc: rusty@...tcorp.com.au, mathieu.desnoyers@...icios.com, oleg@...hat.com, paulmck@...ux.vnet.ibm.com, torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org, andi@...stfloor.org, rostedt@...dmis.org, tglx@...utronix.de, laijs@...fujitsu.com, linux@...izon.com Subject: Re: [PATCH v5 07/10] module: Optimize __module_address() using a latched RB-tree On Mon, Apr 13, 2015 at 06:49:49PM +0200, Ingo Molnar wrote: > * Peter Zijlstra <peterz@...radead.org> wrote: > > +static __always_inline int > > +mod_tree_comp(void *key, struct latch_tree_node *n) > > +{ > > + unsigned long val = (unsigned long)key; > > + unsigned long start, end; > > + > > + end = start = __mod_tree_val(n); > > + end += __mod_tree_size(n); > > + > > + if (val < start) > > + return -1; > > + > > + if (val >= end) > > + return 1; > > + > > + return 0; > > So since we are counting nanoseconds, I suspect this could be written > more optimally as: > > { > unsigned long val = (unsigned long)key; > unsigned long start, end; > > start = __mod_tree_val(n); > if (val < start) > return -1; > > end = start + __mod_tree_size(n); > if (val >= end) > return 1; > > return 0; > } > > right? I was afraid it would rip apart the common bits of __mod_tree_{val,size}(), iow. it would end up doing the whole latch_tree_node -> mod_tree_node -> mod and mtn_init comparison dance twice. But GCC does the right thing, so yes. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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