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[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: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2007-12-24 20:57:56 -08:00 committed by David S. Miller
parent b15c4bcd15
commit 21371f768b
2 changed files with 3 additions and 2 deletions
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3
include/net/sock.h
View File

@ -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)

2
net/core/stream.c
View File

@ -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 &&