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Date: Fri, 11 May 2012 16:42:30 +0200 From: Peter Zijlstra <a.p.zijlstra@...llo.nl> To: Mel Gorman <mgorman@...e.de> Cc: David Miller <davem@...emloft.net>, akpm@...ux-foundation.org, linux-mm@...ck.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, neilb@...e.de, michaelc@...wisc.edu, emunson@...bm.net Subject: Re: [PATCH 10/17] netvm: Allow skb allocation to use PFMEMALLOC reserves On Fri, 2012-05-11 at 15:32 +0100, Mel Gorman wrote: > > > +extern atomic_t memalloc_socks; > > > +static inline int sk_memalloc_socks(void) > > > +{ > > > + return atomic_read(&memalloc_socks); > > > +} > > > > Please change this to be a static branch. > > > > Will do. I renamed memalloc_socks to sk_memalloc_socks, made it a int as > atomics are unnecessary and I check it directly in a branch instead of a > static inline. It should be relatively easy for the branch predictor. David means you to use include/linux/jump_label.h. static struct static_key sk_memalloc_socks = STATIC_KEY_INIT_FALSE; and have your function read: static inline bool sk_memalloc_socks(void) { return static_key_false(&sk_memalloc_socks); } which can be modified using: static_key_slow_inc(&sk_memalloc_socks); or static_key_slow_dec(&sk_memalloc_socks); This magic goo turns the branch into self-modifying code such that the branch is an unconditional jump at runtime. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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