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Commit 21371f76 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

[SOCK] Avoid divides in sk_stream_pages() and __sk_stream_mem_reclaim() 



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: default avatarEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b15c4bcd

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 &&