From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Andrzej Siewior Subject: Re: [PATCH] locking/rtmutex: drop usage of __HAVE_ARCH_CMPXCHG Date: Wed, 25 Feb 2015 18:58:16 +0100 Message-ID: <20150225175816.GF6823@linutronix.de> References: <20150225175613.GE6823@linutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: Arnd Bergmann , Peter Zijlstra , Ingo Molnar , linux-rt-users@vger.kernel.org, will.deacon@arm.com, linux-arm-kernel@lists.infradead.org To: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org Return-path: Content-Disposition: inline In-Reply-To: <20150225175613.GE6823@linutronix.de> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org * Sebastian Andrzej Siewior | 2015-02-25 18:56:13 [+0100]: >To put some numbers on it: preempt -RT, am335x, 10 loops of >100000 invocations of rt_spin_lock() + rt_spin_unlock() (time "total" is >the average of the 10 loops for the 100000 invocations, "loop" is >"total / 100000 * 1000"): This is the test code I was running. diff --git a/init/main.c b/init/main.c index e7cb76c079d4..e74523feeddb 100644 --- a/init/main.c +++ b/init/main.c @@ -1004,6 +1004,29 @@ static noinline void __init kernel_init_freeable(void) do_basic_setup(); + { + spinlock_t main_l; + int loops; + + spin_lock_init(&main_l); + + for (loops = 0; loops < 10; loops++) { + ktime_t start, end; + int i; + + local_irq_disable(); + start = ktime_get(); + for (i = 0; i <= 100000; i++) { + rt_spin_lock(&main_l); + rt_spin_unlock(&main_l); + } + end = ktime_get(); + local_irq_enable(); + pr_err("%s(%d) %lld\n", __func__, __LINE__, + ktime_to_us(ktime_sub(end, start))); + } + } + /* Open the /dev/console on the rootfs, this should never fail */ if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0) pr_err("Warning: unable to open an initial console.\n");