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Message-ID: <20091123124615.GA27808@elte.hu> Date: Mon, 23 Nov 2009 13:46:15 +0100 From: Ingo Molnar <mingo@...e.hu> To: Nick Piggin <npiggin@...e.de> Cc: Peter Zijlstra <peterz@...radead.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: newidle balancing in NUMA domain? * Nick Piggin <npiggin@...e.de> wrote: > > (I hope i explained my point clearly enough.) > > > > No argument that it could be done cleaner - the duality right now of > > both having the fuzzy stats and the rate limiting should be decided > > one way or another. > > Well, I would say please keep domain balancing behaviour at least > somewhat close to how it was with O(1) scheduler at least until CFS is > more sorted out. There is no need to knee jerk because BFS is better > at something. Well, see the change (commit 0ec9fab3d) attached below - even in hindsight it was well argued by Mike with quite a few numbers: +68% in x264 performance. If you think it's a bad change (combined with newidle-rate-limit) then please show the numbers that counter it and preferably extend 'perf bench sched' with the testcases that you care about most. IIRC (and Peter mentioned this too) Mike got into the whole kbuild angle due to comparing mainline scheduler to BFS - but that's really a positive thing IMO, not some "knee-jerk reaction". Ingo -----------------------> >From 0ec9fab3d186d9cbb00c0f694d4a260d07c198d9 Mon Sep 17 00:00:00 2001 From: Mike Galbraith <efault@....de> Date: Tue, 15 Sep 2009 15:07:03 +0200 Subject: [PATCH] sched: Improve latencies and throughput Make the idle balancer more agressive, to improve a x264 encoding workload provided by Jason Garrett-Glaser: NEXT_BUDDY NO_LB_BIAS encoded 600 frames, 252.82 fps, 22096.60 kb/s encoded 600 frames, 250.69 fps, 22096.60 kb/s encoded 600 frames, 245.76 fps, 22096.60 kb/s NO_NEXT_BUDDY LB_BIAS encoded 600 frames, 344.44 fps, 22096.60 kb/s encoded 600 frames, 346.66 fps, 22096.60 kb/s encoded 600 frames, 352.59 fps, 22096.60 kb/s NO_NEXT_BUDDY NO_LB_BIAS encoded 600 frames, 425.75 fps, 22096.60 kb/s encoded 600 frames, 425.45 fps, 22096.60 kb/s encoded 600 frames, 422.49 fps, 22096.60 kb/s Peter pointed out that this is better done via newidle_idx, not via LB_BIAS, newidle balancing should look for where there is load _now_, not where there was load 2 ticks ago. Worst-case latencies are improved as well as no buddies means less vruntime spread. (as per prior lkml discussions) This change improves kbuild-peak parallelism as well. Reported-by: Jason Garrett-Glaser <darkshikari@...il.com> Signed-off-by: Mike Galbraith <efault@....de> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl> LKML-Reference: <1253011667.9128.16.camel@...ge.simson.net> Signed-off-by: Ingo Molnar <mingo@...e.hu> --- arch/ia64/include/asm/topology.h | 5 +++-- arch/powerpc/include/asm/topology.h | 2 +- arch/sh/include/asm/topology.h | 3 ++- arch/x86/include/asm/topology.h | 4 +--- include/linux/topology.h | 2 +- kernel/sched_features.h | 2 +- 6 files changed, 9 insertions(+), 9 deletions(-) diff --git a/arch/ia64/include/asm/topology.h b/arch/ia64/include/asm/topology.h index 47f3c51..42f1673 100644 --- a/arch/ia64/include/asm/topology.h +++ b/arch/ia64/include/asm/topology.h @@ -61,7 +61,7 @@ void build_cpu_to_node_map(void); .cache_nice_tries = 2, \ .busy_idx = 2, \ .idle_idx = 1, \ - .newidle_idx = 2, \ + .newidle_idx = 0, \ .wake_idx = 0, \ .forkexec_idx = 1, \ .flags = SD_LOAD_BALANCE \ @@ -87,10 +87,11 @@ void build_cpu_to_node_map(void); .cache_nice_tries = 2, \ .busy_idx = 3, \ .idle_idx = 2, \ - .newidle_idx = 2, \ + .newidle_idx = 0, \ .wake_idx = 0, \ .forkexec_idx = 1, \ .flags = SD_LOAD_BALANCE \ + | SD_BALANCE_NEWIDLE \ | SD_BALANCE_EXEC \ | SD_BALANCE_FORK \ | SD_BALANCE_WAKE \ diff --git a/arch/powerpc/include/asm/topology.h b/arch/powerpc/include/asm/topology.h index a6b220a..1a2c9eb 100644 --- a/arch/powerpc/include/asm/topology.h +++ b/arch/powerpc/include/asm/topology.h @@ -57,7 +57,7 @@ static inline int pcibus_to_node(struct pci_bus *bus) .cache_nice_tries = 1, \ .busy_idx = 3, \ .idle_idx = 1, \ - .newidle_idx = 2, \ + .newidle_idx = 0, \ .wake_idx = 0, \ .flags = SD_LOAD_BALANCE \ | SD_BALANCE_EXEC \ diff --git a/arch/sh/include/asm/topology.h b/arch/sh/include/asm/topology.h index 9054e5c..c843677 100644 --- a/arch/sh/include/asm/topology.h +++ b/arch/sh/include/asm/topology.h @@ -15,13 +15,14 @@ .cache_nice_tries = 2, \ .busy_idx = 3, \ .idle_idx = 2, \ - .newidle_idx = 2, \ + .newidle_idx = 0, \ .wake_idx = 0, \ .forkexec_idx = 1, \ .flags = SD_LOAD_BALANCE \ | SD_BALANCE_FORK \ | SD_BALANCE_EXEC \ | SD_BALANCE_WAKE \ + | SD_BALANCE_NEWIDLE \ | SD_SERIALIZE, \ .last_balance = jiffies, \ .balance_interval = 1, \ diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h index 4b1b335..7fafd1b 100644 --- a/arch/x86/include/asm/topology.h +++ b/arch/x86/include/asm/topology.h @@ -116,14 +116,12 @@ extern unsigned long node_remap_size[]; # define SD_CACHE_NICE_TRIES 1 # define SD_IDLE_IDX 1 -# define SD_NEWIDLE_IDX 2 # define SD_FORKEXEC_IDX 0 #else # define SD_CACHE_NICE_TRIES 2 # define SD_IDLE_IDX 2 -# define SD_NEWIDLE_IDX 2 # define SD_FORKEXEC_IDX 1 #endif @@ -137,7 +135,7 @@ extern unsigned long node_remap_size[]; .cache_nice_tries = SD_CACHE_NICE_TRIES, \ .busy_idx = 3, \ .idle_idx = SD_IDLE_IDX, \ - .newidle_idx = SD_NEWIDLE_IDX, \ + .newidle_idx = 0, \ .wake_idx = 0, \ .forkexec_idx = SD_FORKEXEC_IDX, \ \ diff --git a/include/linux/topology.h b/include/linux/topology.h index c87edcd..4298745 100644 --- a/include/linux/topology.h +++ b/include/linux/topology.h @@ -151,7 +151,7 @@ int arch_update_cpu_topology(void); .cache_nice_tries = 1, \ .busy_idx = 2, \ .idle_idx = 1, \ - .newidle_idx = 2, \ + .newidle_idx = 0, \ .wake_idx = 0, \ .forkexec_idx = 1, \ \ diff --git a/kernel/sched_features.h b/kernel/sched_features.h index 891ea0f..e98c2e8 100644 --- a/kernel/sched_features.h +++ b/kernel/sched_features.h @@ -67,7 +67,7 @@ SCHED_FEAT(AFFINE_WAKEUPS, 1) * wakeup-preemption), since its likely going to consume data we * touched, increases cache locality. */ -SCHED_FEAT(NEXT_BUDDY, 1) +SCHED_FEAT(NEXT_BUDDY, 0) /* * Prefer to schedule the task that ran last (when we did -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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