From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754787Ab2E2SRO (ORCPT ); Tue, 29 May 2012 14:17:14 -0400 Received: from perches-mx.perches.com ([206.117.179.246]:59227 "EHLO labridge.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754963Ab2E2SRM (ORCPT ); Tue, 29 May 2012 14:17:12 -0400 Message-ID: <1338315431.18974.10.camel@joe2Laptop> Subject: [PATCH] printk: Shrink printk_sched buffer size, eliminate it when !CONFIG_PRINTK From: Joe Perches To: Ingo Molnar Cc: Peter Zijlstra , Linus Torvalds , Andrew Morton , Kay Sievers , LKML Date: Tue, 29 May 2012 11:17:11 -0700 In-Reply-To: <20120523155003.GA8202@gmail.com> References: <1337086834.27020.162.camel@laptop> <1337096141.27694.82.camel@twins> <1337193010.27694.146.camel@twins> <1337468148.573.139.camel@twins> <20120523150359.GB26974@gmail.com> <1337787838.1734.15.camel@joe2Laptop> <20120523155003.GA8202@gmail.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.2- Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The size of the per-cpu printk_sched buf is much larger than necessary. The maximum sched message emitted is ~80 bytes. Shrink the allocation for this printk_sched buffer from 512 bytes to 128. printk_sched creates an unnecessary per-cpu buffer when CONFIG_PRINTK is not enabled. Remove it when appropriate so embedded uses save a bit of space too. Signed-off-by: Joe Perches --- kernel/printk.c | 14 ++++++++++---- 1 files changed, 10 insertions(+), 4 deletions(-) diff --git a/kernel/printk.c b/kernel/printk.c index 32462d2..61cff0b 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -1726,24 +1726,30 @@ int is_console_locked(void) } /* - * Delayed printk version, for scheduler-internal messages: + * Delayed printk version, for scheduler-internal messages. + * Not the normal 512 as it's a bit wasteful, sched messages are short, + * and 128 is more than sufficient for all current messages. */ -#define PRINTK_BUF_SIZE 512 +#define PRINTK_SCHED_BUF_SIZE 128 #define PRINTK_PENDING_WAKEUP 0x01 #define PRINTK_PENDING_SCHED 0x02 static DEFINE_PER_CPU(int, printk_pending); -static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf); +#ifdef CONFIG_PRINTK +static DEFINE_PER_CPU(char [PRINTK_SCHED_BUF_SIZE], printk_sched_buf); +#endif void printk_tick(void) { if (__this_cpu_read(printk_pending)) { int pending = __this_cpu_xchg(printk_pending, 0); +#ifdef CONFIG_PRINTK if (pending & PRINTK_PENDING_SCHED) { char *buf = __get_cpu_var(printk_sched_buf); printk(KERN_WARNING "[sched_delayed] %s", buf); } +#endif if (pending & PRINTK_PENDING_WAKEUP) wake_up_interruptible(&log_wait); } @@ -2189,7 +2195,7 @@ int printk_sched(const char *fmt, ...) buf = __get_cpu_var(printk_sched_buf); va_start(args, fmt); - r = vsnprintf(buf, PRINTK_BUF_SIZE, fmt, args); + r = vsnprintf(buf, PRINTK_SCHED_BUF_SIZE, fmt, args); va_end(args); __this_cpu_or(printk_pending, PRINTK_PENDING_SCHED);