Re: [PATCH 10/17] netvm: Allow skb allocation to use PFMEMALLOC reserves

On Fri, 2012-05-11 at 15:32 +0100, Mel Gorman wrote:

quoted

quoted

+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.

  

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