[v2] sched: Reduce the default slice to avoid tasks getting an extra tick

[PATCH V2 2/2] sched: Reduce the default slice to avoid tasks getting an extra tick

Posted by zihan zhou 1 year ago

update sysctl_sched_base_slice with debugfs, limit its value and
update normalized_sysctl_sched_base_slice.

Signed-off-by: zihan zhou <15645113830zzh@gmail.com>
---
 kernel/sched/debug.c | 51 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 50 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index fd7e85220715..70dda949a69a 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -166,6 +166,55 @@ static const struct file_operations sched_feat_fops = {
 	.release	= single_release,
 };
 
+
+static ssize_t sched_base_slice_write(struct file *filp, const char __user *ubuf,
+				   size_t cnt, loff_t *ppos)
+{
+	char buf[16];
+	unsigned int base_slice;
+
+	if (cnt > 15)
+		cnt = 15;
+
+	if (copy_from_user(&buf, ubuf, cnt))
+		return -EFAULT;
+	buf[cnt] = '\0';
+
+	if (kstrtouint(buf, 10, &base_slice))
+		return -EINVAL;
+
+
+	base_slice = clamp_t(u64, base_slice,
+					NSEC_PER_MSEC/10,   /* HZ=1000 * 10 */
+					NSEC_PER_MSEC*100); /* HZ=100  / 10 */
+
+	sysctl_sched_base_slice = base_slice;
+
+	sched_update_scaling();
+
+	*ppos += cnt;
+	return cnt;
+}
+
+static int sched_base_slice_show(struct seq_file *m, void *v)
+{
+	seq_printf(m, "%d\n", sysctl_sched_base_slice);
+	return 0;
+}
+
+static int sched_base_slice_open(struct inode *inode, struct file *filp)
+{
+	return single_open(filp, sched_base_slice_show, NULL);
+}
+
+static const struct file_operations sched_base_slice_fops = {
+	.open		= sched_base_slice_open,
+	.write		= sched_base_slice_write,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
 #ifdef CONFIG_SMP
 
 static ssize_t sched_scaling_write(struct file *filp, const char __user *ubuf,
@@ -505,7 +554,7 @@ static __init int sched_init_debug(void)
 	debugfs_create_file("preempt", 0644, debugfs_sched, NULL, &sched_dynamic_fops);
 #endif
 
-	debugfs_create_u32("base_slice_ns", 0644, debugfs_sched, &sysctl_sched_base_slice);
+	debugfs_create_file("base_slice_ns", 0644, debugfs_sched, NULL, &sched_base_slice_fops);
 
 	debugfs_create_u32("latency_warn_ms", 0644, debugfs_sched, &sysctl_resched_latency_warn_ms);
 	debugfs_create_u32("latency_warn_once", 0644, debugfs_sched, &sysctl_resched_latency_warn_once);
-- 
2.33.0

Re: [PATCH V2 2/2] sched: Reduce the default slice to avoid tasks getting an extra tick

Posted by kernel test robot 1 year ago

Hi zihan,

kernel test robot noticed the following build errors:

[auto build test ERROR on tip/sched/core]
[also build test ERROR on peterz-queue/sched/core linus/master v6.14-rc1 next-20250207]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/zihan-zhou/sched-Reduce-the-default-slice-to-avoid-tasks-getting-an-extra-tick/20250207-142556
base:   tip/sched/core
patch link:    https://lore.kernel.org/r/20250207062402.33725-1-15645113830zzh%40gmail.com
patch subject: [PATCH V2 2/2] sched: Reduce the default slice to avoid tasks getting an extra tick
config: x86_64-randconfig-072-20250208 (https://download.01.org/0day-ci/archive/20250208/202502081304.ujyIUca2-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250208/202502081304.ujyIUca2-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202502081304.ujyIUca2-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from kernel/sched/build_utility.c:72:
   kernel/sched/debug.c: In function 'sched_base_slice_write':
>> kernel/sched/debug.c:193:9: error: implicit declaration of function 'sched_update_scaling'; did you mean 'sched_update_numa'? [-Werror=implicit-function-declaration]
     193 |         sched_update_scaling();
         |         ^~~~~~~~~~~~~~~~~~~~
         |         sched_update_numa
   cc1: some warnings being treated as errors


vim +193 kernel/sched/debug.c

   168	
   169	
   170	static ssize_t sched_base_slice_write(struct file *filp, const char __user *ubuf,
   171					   size_t cnt, loff_t *ppos)
   172	{
   173		char buf[16];
   174		unsigned int base_slice;
   175	
   176		if (cnt > 15)
   177			cnt = 15;
   178	
   179		if (copy_from_user(&buf, ubuf, cnt))
   180			return -EFAULT;
   181		buf[cnt] = '\0';
   182	
   183		if (kstrtouint(buf, 10, &base_slice))
   184			return -EINVAL;
   185	
   186	
   187		base_slice = clamp_t(u64, base_slice,
   188						NSEC_PER_MSEC/10,   /* HZ=1000 * 10 */
   189						NSEC_PER_MSEC*100); /* HZ=100  / 10 */
   190	
   191		sysctl_sched_base_slice = base_slice;
   192	
 > 193		sched_update_scaling();
   194	
   195		*ppos += cnt;
   196		return cnt;
   197	}
   198	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH V2 2/2] sched: Reduce the default slice to avoid tasks getting an extra tick

Posted by kernel test robot 1 year ago

Hi zihan,

kernel test robot noticed the following build errors:

[auto build test ERROR on tip/sched/core]
[also build test ERROR on peterz-queue/sched/core linus/master v6.14-rc1 next-20250207]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/zihan-zhou/sched-Reduce-the-default-slice-to-avoid-tasks-getting-an-extra-tick/20250207-142556
base:   tip/sched/core
patch link:    https://lore.kernel.org/r/20250207062402.33725-1-15645113830zzh%40gmail.com
patch subject: [PATCH V2 2/2] sched: Reduce the default slice to avoid tasks getting an extra tick
config: i386-randconfig-141-20250208 (https://download.01.org/0day-ci/archive/20250208/202502080831.VwRnAlxo-lkp@intel.com/config)
compiler: clang version 19.1.3 (https://github.com/llvm/llvm-project ab51eccf88f5321e7c60591c5546b254b6afab99)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250208/202502080831.VwRnAlxo-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202502080831.VwRnAlxo-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from kernel/sched/build_utility.c:72:
>> kernel/sched/debug.c:193:2: error: call to undeclared function 'sched_update_scaling'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     193 |         sched_update_scaling();
         |         ^
   1 error generated.


vim +/sched_update_scaling +193 kernel/sched/debug.c

   168	
   169	
   170	static ssize_t sched_base_slice_write(struct file *filp, const char __user *ubuf,
   171					   size_t cnt, loff_t *ppos)
   172	{
   173		char buf[16];
   174		unsigned int base_slice;
   175	
   176		if (cnt > 15)
   177			cnt = 15;
   178	
   179		if (copy_from_user(&buf, ubuf, cnt))
   180			return -EFAULT;
   181		buf[cnt] = '\0';
   182	
   183		if (kstrtouint(buf, 10, &base_slice))
   184			return -EINVAL;
   185	
   186	
   187		base_slice = clamp_t(u64, base_slice,
   188						NSEC_PER_MSEC/10,   /* HZ=1000 * 10 */
   189						NSEC_PER_MSEC*100); /* HZ=100  / 10 */
   190	
   191		sysctl_sched_base_slice = base_slice;
   192	
 > 193		sched_update_scaling();
   194	
   195		*ppos += cnt;
   196		return cnt;
   197	}
   198	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki