[SOCK] Avoid divides in sk_stream_pages() and __sk_stream_mem_reclaim() (21371f76) · Commits · 戴 / test

sk_forward_alloc being signed, we should take care of divides by SK_STREAM_MEM_QUANTUM we do in sk_stream_pages() and __sk_stream_mem_reclaim() This patchs introduces SK_STREAM_MEM_QUANTUM_SHIFT, defined as ilog2(SK_STREAM_MEM_QUANTUM), to be able to use right shifts instead of plain divides. This should help compiler to choose right shifts instead of expensive divides (as seen with CONFIG_CC_OPTIMIZE_FOR_SIZE=y on x86) Signed-off-by:

Eric Dumazet <dada1@cosmosbay.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

include/net/sock.h

+2 −1

Original line number	Diff line number	Diff line
		@@ -716,10 +716,11 @@ extern void __sk_stream_mem_reclaim(struct sock *sk);
		extern int sk_stream_mem_schedule(struct sock *sk, int size, int kind);

		#define SK_STREAM_MEM_QUANTUM ((int)PAGE_SIZE)
		#define SK_STREAM_MEM_QUANTUM_SHIFT ilog2(SK_STREAM_MEM_QUANTUM)

		static inline int sk_stream_pages(int amt)
		{
		return DIV_ROUND_UP(amt, SK_STREAM_MEM_QUANTUM);
		return (amt + SK_STREAM_MEM_QUANTUM - 1) >> SK_STREAM_MEM_QUANTUM_SHIFT;
		}

		static inline void sk_stream_mem_reclaim(struct sock *sk)

net/core/stream.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -196,7 +196,7 @@ EXPORT_SYMBOL(sk_stream_error);

		void __sk_stream_mem_reclaim(struct sock *sk)
		{
		atomic_sub(sk->sk_forward_alloc / SK_STREAM_MEM_QUANTUM,
		atomic_sub(sk->sk_forward_alloc >> SK_STREAM_MEM_QUANTUM_SHIFT,
		sk->sk_prot->memory_allocated);
		sk->sk_forward_alloc &= SK_STREAM_MEM_QUANTUM - 1;
		if (*sk->sk_prot->memory_pressure &&

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