From: Rik van Riel <r...@redhat.com>

The previous patch makes it so the code skips over isolcpus when
building scheduler load balancing domains. This makes it hard to
see for a user which of the CPUs in a cpuset are participating in
load balancing, and which ones are isolated cpus.

Add a cpuset.isolcpus file with info on which cpus in a cpuset are
isolated CPUs.

This file is read-only for now. In the future we could extend things
so isolcpus can be changed at run time, for the root (system wide)
cpuset only.

Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Clark Williams <willi...@redhat.com>
Cc: Li Zefan <lize...@huawei.com>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: Luiz Capitulino <lcapitul...@redhat.com>
Cc: David Rientjes <rient...@google.com>
Cc: Mike Galbraith <umgwanakikb...@gmail.com>
Cc: cgro...@vger.kernel.org
Signed-off-by: Rik van Riel <r...@redhat.com>
---
 kernel/cpuset.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index b544e5229d99..94bf59588e23 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1563,6 +1563,7 @@ typedef enum {
        FILE_MEMORY_PRESSURE,
        FILE_SPREAD_PAGE,
        FILE_SPREAD_SLAB,
+       FILE_ISOLCPUS,
 } cpuset_filetype_t;
 
 static int cpuset_write_u64(struct cgroup_subsys_state *css, struct cftype 
*cft,
@@ -1704,6 +1705,20 @@ static ssize_t cpuset_write_resmask(struct 
kernfs_open_file *of,
        return retval ?: nbytes;
 }
 
+static void cpuset_seq_print_isolcpus(struct seq_file *sf, struct cpuset *cs)
+{
+       cpumask_var_t my_isolated_cpus;
+
+       if (!alloc_cpumask_var(&my_isolated_cpus, GFP_KERNEL))
+               return;
+
+       cpumask_and(my_isolated_cpus, cs->cpus_allowed, cpu_isolated_map);
+
+       seq_printf(sf, "%*pbl\n", nodemask_pr_args(my_isolated_cpus));
+
+       free_cpumask_var(my_isolated_cpus);
+}
+
 /*
  * These ascii lists should be read in a single call, by using a user
  * buffer large enough to hold the entire map.  If read in smaller
@@ -1733,6 +1748,9 @@ static int cpuset_common_seq_show(struct seq_file *sf, 
void *v)
        case FILE_EFFECTIVE_MEMLIST:
                seq_printf(sf, "%*pbl\n", 
nodemask_pr_args(&cs->effective_mems));
                break;
+       case FILE_ISOLCPUS:
+               cpuset_seq_print_isolcpus(sf, cs);
+               break;
        default:
                ret = -EINVAL;
        }
@@ -1893,6 +1911,12 @@ static struct cftype files[] = {
                .private = FILE_MEMORY_PRESSURE_ENABLED,
        },
 
+       {
+               .name = "isolcpus",
+               .seq_show = cpuset_common_seq_show,
+               .private = FILE_ISOLCPUS,
+       },
+
        { }     /* terminate */
 };
 
-- 
2.1.0

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