From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [SOCK] Avoid divides in sk_stream_pages() and __sk_stream_mem_reclaim() Date: Fri, 21 Dec 2007 15:45:08 +0100 Message-ID: <20071221154508.97aef5d9.dada1@cosmosbay.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: "netdev@vger.kernel.org" To: David Miller Return-path: Received: from pfx2.jmh.fr ([194.153.89.55]:53835 "EHLO pfx2.jmh.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751286AbXLUOpM (ORCPT ); Fri, 21 Dec 2007 09:45:12 -0500 Sender: netdev-owner@vger.kernel.org List-ID: Hi David This is the last one of this boring patch suite. I prefered to not change sk_forward_alloc type, I prefer to wait 18 months more before taking this responsibility :) Merry Christmas everybody Eric [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 diff --git a/include/net/sock.h b/include/net/sock.h index 4456453..a134be1 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -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) diff --git a/net/core/stream.c b/net/core/stream.c index 5586879..bf188ff 100644 --- a/net/core/stream.c +++ b/net/core/stream.c @@ -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 &&