Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752475AbYLHILG (ORCPT ); Mon, 8 Dec 2008 03:11:06 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751268AbYLHIKy (ORCPT ); Mon, 8 Dec 2008 03:10:54 -0500 Received: from gw1.cosmosbay.com ([86.65.150.130]:45575 "EHLO gw1.cosmosbay.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750848AbYLHIKx convert rfc822-to-8bit (ORCPT ); Mon, 8 Dec 2008 03:10:53 -0500 Message-ID: <493CD530.4020808@cosmosbay.com> Date: Mon, 08 Dec 2008 09:05:04 +0100 From: Eric Dumazet User-Agent: Thunderbird 2.0.0.18 (Windows/20081105) MIME-Version: 1.0 To: Andrew Morton CC: Peter Zijlstra , Mike Travis , "David S. Miller" , linux kernel , Christoph Lameter , linux-ext4@vger.kernel.org Subject: [PATCH] percpu_counter: FBC_BATCH should be a variable References: <4939513C.3090101@cosmosbay.com> <493B9699.8080603@cosmosbay.com> <20081207090918.595627b2.akpm@linux-foundation.org> <493C1632.2000901@cosmosbay.com> <20081207203244.10372834.akpm@linux-foundation.org> In-Reply-To: <20081207203244.10372834.akpm@linux-foundation.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-1.6 (gw1.cosmosbay.com [0.0.0.0]); Mon, 08 Dec 2008 09:05:09 +0100 (CET) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6186 Lines: 181 Andrew Morton a ?crit : > On Sun, 07 Dec 2008 19:30:10 +0100 Eric Dumazet wrote: > >>> Do >>> >>> $EDITOR $(grep -l hotcpu_notifier */*.c) >>> >>> and you'll see lots of code gets it right, and lots of code gets it wrong. >> I see nothing interesting, I must be blind. >> >> lib/percpu_counter.c: In function 'percpu_counter_startup': >> lib/percpu_counter.c:158: error: 'percpu_counter_hotcpu_callback' undeclared (first use in this function) >> lib/percpu_counter.c:158: error: (Each undeclared identifier is reported only once >> lib/percpu_counter.c:158: error: for each function it appears in.) >> make[1]: *** [lib/percpu_counter.o] Error 1 > > Perhaps you still had percpu_counter_hotcpu_callback inside #ifdef. > > That a look at kernel/workqueue.c, fs/buffer.c. No #ifdef CONFIG_HOTPLUG_CPU > needed at all. We still need some #ifdef or we also must also delete them around "struct list_head list" in include/linux/percpu_counter.h and grow struct percpu_counter. lib/percpu_counter.c: In function 'percpu_counter_hotcpu_callback': lib/percpu_counter.c:137: error: 'struct percpu_counter' has no member named 'list' lib/percpu_counter.c:137: warning: type defaults to 'int' in declaration of '__mptr' lib/percpu_counter.c:137: warning: initialization from incompatible pointer type ... Thank you Andrew [PATCH] percpu_counter: FBC_BATCH should be a variable For NR_CPUS >= 16 values, FBC_BATCH is 2*NR_CPUS Considering more and more distros are using high NR_CPUS values, it makes sense to use a more sensible value for FBC_BATCH, and get rid of NR_CPUS. A sensible value is 2*num_online_cpus(), with a minimum value of 32 (This minimum value helps branch prediction in __percpu_counter_add()) We already have a hotcpu notifier, so we can adjust FBC_BATCH dynamically. We rename FBC_BATCH to percpu_counter_batch since its not a constant anymore. Signed-off-by: Eric Dumazet Acked-by: David S. Miller Acked-by: Peter Zijlstra --- fs/ext4/ext4.h | 6 +++--- fs/ext4/inode.c | 2 +- include/linux/percpu_counter.h | 8 ++------ lib/percpu_counter.c | 18 ++++++++++++++---- 4 files changed, 20 insertions(+), 14 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index b0537c8..6c46c64 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -1225,11 +1225,11 @@ do { \ } while (0) #ifdef CONFIG_SMP -/* Each CPU can accumulate FBC_BATCH blocks in their local +/* Each CPU can accumulate percpu_counter_batch blocks in their local * counters. So we need to make sure we have free blocks more - * than FBC_BATCH * nr_cpu_ids. Also add a window of 4 times. + * than percpu_counter_batch * nr_cpu_ids. Also add a window of 4 times. */ -#define EXT4_FREEBLOCKS_WATERMARK (4 * (FBC_BATCH * nr_cpu_ids)) +#define EXT4_FREEBLOCKS_WATERMARK (4 * (percpu_counter_batch * nr_cpu_ids)) #else #define EXT4_FREEBLOCKS_WATERMARK 0 #endif diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index be21a5a..db661e7 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2497,7 +2497,7 @@ static int ext4_nonda_switch(struct super_block *sb) /* * switch to non delalloc mode if we are running low * on free block. The free block accounting via percpu - * counters can get slightly wrong with FBC_BATCH getting + * counters can get slightly wrong with percpu_counter_batch getting * accumulated on each CPU without updating global counters * Delalloc need an accurate free block accounting. So switch * to non delalloc when we are near to error range. diff --git a/include/linux/percpu_counter.h b/include/linux/percpu_counter.h index 9007ccd..99de7a3 100644 --- a/include/linux/percpu_counter.h +++ b/include/linux/percpu_counter.h @@ -24,11 +24,7 @@ struct percpu_counter { s32 *counters; }; -#if NR_CPUS >= 16 -#define FBC_BATCH (NR_CPUS*2) -#else -#define FBC_BATCH (NR_CPUS*4) -#endif +extern int percpu_counter_batch; int percpu_counter_init(struct percpu_counter *fbc, s64 amount); int percpu_counter_init_irq(struct percpu_counter *fbc, s64 amount); @@ -39,7 +35,7 @@ s64 __percpu_counter_sum(struct percpu_counter *fbc); static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount) { - __percpu_counter_add(fbc, amount, FBC_BATCH); + __percpu_counter_add(fbc, amount, percpu_counter_batch); } static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc) diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c index a866389..e73eb5b 100644 --- a/lib/percpu_counter.c +++ b/lib/percpu_counter.c @@ -9,10 +9,8 @@ #include #include -#ifdef CONFIG_HOTPLUG_CPU static LIST_HEAD(percpu_counters); static DEFINE_MUTEX(percpu_counters_lock); -#endif void percpu_counter_set(struct percpu_counter *fbc, s64 amount) { @@ -114,13 +112,24 @@ void percpu_counter_destroy(struct percpu_counter *fbc) } EXPORT_SYMBOL(percpu_counter_destroy); -#ifdef CONFIG_HOTPLUG_CPU +int percpu_counter_batch __read_mostly = 32; +EXPORT_SYMBOL(percpu_counter_batch); + +static void compute_batch_value(void) +{ + int nr = num_online_cpus(); + + percpu_counter_batch = max(32, nr*2); +} + static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb, unsigned long action, void *hcpu) { +#ifdef CONFIG_HOTPLUG_CPU unsigned int cpu; struct percpu_counter *fbc; + compute_batch_value(); if (action != CPU_DEAD) return NOTIFY_OK; @@ -137,13 +146,14 @@ static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb, spin_unlock_irqrestore(&fbc->lock, flags); } mutex_unlock(&percpu_counters_lock); +#endif return NOTIFY_OK; } static int __init percpu_counter_startup(void) { + compute_batch_value(); hotcpu_notifier(percpu_counter_hotcpu_callback, 0); return 0; } module_init(percpu_counter_startup); -#endif -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/