From: Gao Xiang <gaoxiang25@huawei.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>,
Kate Stewart <kstewart@linuxfoundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
"Will Deacon" <will.deacon@arm.com>,
<linux-kernel@vger.kernel.org>, Miao Xie <miaoxie@huawei.com>,
Chao Yu <chao@kernel.org>
Subject: Re: [PATCH v2] bit_spinlock: introduce smp_cond_load_relaxed
Date: Tue, 30 Oct 2018 13:52:13 +0800 [thread overview]
Message-ID: <3455f753-8f7c-91a8-c926-e06f5ed2d1bb@huawei.com> (raw)
In-Reply-To: <20181030060441.16107-1-gaoxiang25@huawei.com>
Hi,
On 2018/10/30 14:04, Gao Xiang wrote:
> It is better to use wrapped smp_cond_load_relaxed
> instead of open-coded busy waiting for bit_spinlock.
>
> Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
> ---
>
> change log v2:
> - fix the incorrect expression !(VAL >> (bitnum & (BITS_PER_LONG-1)))
> - the test result is described in the following reply.
>
> Thanks,
> Gao Xiang
Simple test script:
#include <linux/kthread.h>
#include <linux/bit_spinlock.h>
#include <linux/module.h>
unsigned long global_lock;
int test_thread(void *data)
{
unsigned long thread_id = (unsigned long)data;
int i;
u64 start = ktime_get_ns();
for (i = 0; i < 500000; ++i) {
bit_spin_lock(0, &global_lock);
__asm__("yield");
bit_spin_unlock(0, &global_lock);
}
pr_err("Thread id: %lu time: %llu\n", thread_id, ktime_get_ns() - start);
do_exit(0);
}
static int __init bitspinlock_test_module_init(void)
{
int i;
for (i = 0; i < 8; ++i) {
if (IS_ERR(kthread_run(test_thread, (void *)(unsigned long)i, "thread-%d", i)))
pr_err("fail to create thread %d\n", i);
}
return 0;
}
static void __exit bitspinlock_test_module_exit(void)
{
}
module_init(bitspinlock_test_module_init);
module_exit(bitspinlock_test_module_exit);
MODULE_LICENSE("GPL");
...and tested in the following ARM server environment:
Processor: HI1616 (https://en.wikichip.org/wiki/hisilicon/hi16xx/hi1616)
Board: HiSilicon D05 Development Board (http://open-estuary.org/d05/)
Memory: 512GB
Host OS: Ubuntu 18.04.1 LTS (Ubuntu 4.15.0-29.31-generic 4.15.18)
QEMU KVM OS: Linux 4.19 + buildroot
QEMU KVM cmdline: qemu-system-aarch64 -enable-kvm -cpu host -smp 4 -m 256M -kernel Image -M virt,kernel_irqchip=on -nographic -hda rootfs.ext2 -append 'root=/dev/vda console=ttyAMA0 earlycon=pl011,0x9000000' -serial mon:stdio -net none
Without this patch:
Thread 0 Thread 1 Thread 2 Thread 3 Thread 4 Thread 5 Thread 6 Thread 7
1 1283709480 1271869280 454742480 1173673820 1145643640 1118846920 774616920 1144146140
2 643580180 625143860 576841700 322982340 649987880 585749000 529178880 373374780
3 672307220 847315000 880801860 1039502040 667086380 1033939940 1035381120 1046898300
4 568635580 440547020 737000380 910040880 804543740 712314280 868896880 867049000
5 749107320 726397720 776134480 611970100 756721040 753449440 711691300 609343300
With this patch:
Thread 0 Thread 1 Thread 2 Thread 3 Thread 4 Thread 5 Thread 6 Thread 7
1 170327620 196322160 169434180 74723860 178145600 178873460 143843260 70998780
2 166415220 129649200 166161240 175241520 155474460 112811860 157003140 150087420
3 511420780 117655640 598641860 596213720 462888760 430838600 554346300 428035120
4 174520240 156311800 120274280 87465380 172781400 136118620 163728340 63026360
5 153677940 202786860 183626500 140721300 150311360 161266840 168154340 107247460
Thanks,
Gao Xiang
next prev parent reply other threads:[~2018-10-30 5:52 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-13 6:47 [RFC PATCH] bit_spinlock: introduce smp_cond_load_relaxed Gao Xiang
2018-10-13 7:04 ` Greg Kroah-Hartman
2018-10-13 7:22 ` Gao Xiang
2018-10-13 7:30 ` Greg Kroah-Hartman
2018-10-13 7:44 ` Gao Xiang
2018-10-13 7:30 ` Gao Xiang
2018-10-30 6:04 ` [PATCH v2] " Gao Xiang
2018-10-30 5:52 ` Gao Xiang [this message]
2018-11-05 17:11 ` Gao Xiang
2018-11-05 22:49 ` Will Deacon
2018-11-06 1:45 ` Gao Xiang
2018-11-06 9:06 ` Peter Zijlstra
2018-11-06 10:22 ` Gao Xiang
2018-11-06 11:00 ` Peter Zijlstra
2018-11-06 11:36 ` Gao Xiang
2018-11-06 12:27 ` Peter Zijlstra
2018-11-06 12:33 ` Gao Xiang
2018-11-06 12:38 ` Gao Xiang
2018-11-06 12:43 ` Peter Zijlstra
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