Re: [RFC][PATCH v5 05/14] sched: add a packing level knob

On 12 November 2013 11:32, Peter Zijlstra peterz@infradead.org wrote:

On Fri, Oct 18, 2013 at 01:52:18PM +0200, Vincent Guittot wrote:

...

+int sched_proc_update_packing(struct ctl_table *table, int write,

•         void __user *buffer, size_t *lenp,
  

•         loff_t *ppos)
  

+{

• int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
  

• if (ret || !write)
  

•         return ret;
  

• if (sysctl_sched_packing_level)
  

•         sd_pack_threshold = (100 * 1024) / sysctl_sched_packing_level;
  

• return 0;
  

+}

...

+#ifdef CONFIG_SCHED_PACKING_TASKS +static int min_sched_packing_level; +static int max_sched_packing_level = 100; +#endif /* CONFIG_SMP */

...

+#ifdef CONFIG_SCHED_PACKING_TASKS

• {
  

•         .procname       = "sched_packing_level",
  

•         .data           = &sysctl_sched_packing_level,
  

•         .maxlen         = sizeof(int),
  

•         .mode           = 0644,
  

•         .proc_handler   = sched_proc_update_packing,
  

•         .extra1         = &min_sched_packing_level,
  

•         .extra2         = &max_sched_packing_level,
  

• },
  

+#endif

Shouldn't min_sched_packing_level be 1? Userspace can now write 0 and expect something; but then we don't update sd_pack_threshold so nothing really changed.

value 0 is used to disable to packing feature and the scheduler falls back to default behavior. This value is tested when setting which cpus will be used by the scheduler.