From mboxrd@z Thu Jan 1 00:00:00 1970 From: akpm@linux-foundation.org Subject: - sched-avoid-div-in-rebalance_tick.patch removed from -mm tree Date: Mon, 12 Feb 2007 14:47:22 -0800 Message-ID: <200702122247.l1CMlMZ6013909@shell0.pdx.osdl.net> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from smtp.osdl.org ([65.172.181.24]:45373 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965439AbXBLWrm (ORCPT ); Mon, 12 Feb 2007 17:47:42 -0500 Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: npiggin@suse.de, alan@lxorguk.ukuu.org.uk, mingo@elte.hu, mm-commits@vger.kernel.org The patch titled sched: avoid div in rebalance_tick has been removed from the -mm tree. Its filename was sched-avoid-div-in-rebalance_tick.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ Subject: sched: avoid div in rebalance_tick From: Nick Piggin Avoid expensive integer divide 3 times per CPU per tick. A userspace test of this loop went from 26ns, down to 19ns on a G5; and from 123ns down to 28ns on a P3. (Also avoid a variable bit shift, as suggested by Alan. The effect of this wasn't noticable on the CPUs I tested with). Signed-off-by: Nick Piggin Cc: Ingo Molnar Cc: Alan Cox Signed-off-by: Andrew Morton --- kernel/sched.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff -puN kernel/sched.c~sched-avoid-div-in-rebalance_tick kernel/sched.c --- a/kernel/sched.c~sched-avoid-div-in-rebalance_tick +++ a/kernel/sched.c @@ -2897,14 +2897,16 @@ static void active_load_balance(struct r static void update_load(struct rq *this_rq) { unsigned long this_load; - int i, scale; + unsigned int i, scale; this_load = this_rq->raw_weighted_load; /* Update our load: */ - for (i = 0, scale = 1; i < 3; i++, scale <<= 1) { + for (i = 0, scale = 1; i < 3; i++, scale += scale) { unsigned long old_load, new_load; + /* scale is effectively 1 << i now, and >> i divides by scale */ + old_load = this_rq->cpu_load[i]; new_load = this_load; /* @@ -2914,7 +2916,7 @@ static void update_load(struct rq *this_ */ if (new_load > old_load) new_load += scale-1; - this_rq->cpu_load[i] = (old_load*(scale-1) + new_load) / scale; + this_rq->cpu_load[i] = (old_load*(scale-1) + new_load) >> i; } } _ Patches currently in -mm which might be from npiggin@suse.de are origin.patch git-block.patch fs-fix-__block_write_full_page-error-case-buffer-submission.patch