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Subject[PATCH] Dynamically allocate struct mem_cgroup_stat_cpu memory
When increasing NR_CPUS to 4096 the size of struct mem_cgroup is growing to
507904 bytes per instance on x86_64. This patch changes the allocation of
struct mem_cgroup_stat_cpu to be based on the number of configured CPUs during
boot time. The init_mem_cgroup still is that huge since it stays statically
allocated and therefore uses the compile-time maximum.

Signed-off-by: Jan Blunck <jblunck@suse.de>
---
mm/memcontrol.c | 52 +++++++++++++++++++++++++++++++++++++++++++---------
1 file changed, 43 insertions(+), 9 deletions(-)

Index: b/mm/memcontrol.c
===================================================================
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -59,7 +59,7 @@ struct mem_cgroup_stat_cpu {
} ____cacheline_aligned_in_smp;

struct mem_cgroup_stat {
- struct mem_cgroup_stat_cpu cpustat[NR_CPUS];
+ struct mem_cgroup_stat_cpu *cpustat;
};

/*
@@ -142,7 +142,10 @@ struct mem_cgroup {
*/
struct mem_cgroup_stat stat;
};
-static struct mem_cgroup init_mem_cgroup;
+static struct mem_cgroup_stat_cpu init_mem_cgroup_stat_cpu[NR_CPUS];
+static struct mem_cgroup init_mem_cgroup = {
+ .stat = { .cpustat = init_mem_cgroup_stat_cpu },
+};

/*
* We use the lower bit of the page->page_cgroup pointer as a bit spin
@@ -1097,23 +1100,54 @@ static void free_mem_cgroup_per_zone_inf
static struct mem_cgroup *mem_cgroup_alloc(void)
{
struct mem_cgroup *mem;
+ struct mem_cgroup_stat_cpu *cpustat;
+ size_t statsize = nr_cpu_ids * sizeof(*cpustat);

- if (sizeof(*mem) < PAGE_SIZE)
- mem = kmalloc(sizeof(*mem), GFP_KERNEL);
- else
+ if (sizeof(*mem) > PAGE_SIZE) {
mem = vmalloc(sizeof(*mem));
-
- if (mem)
+ if (!mem)
+ goto out;
memset(mem, 0, sizeof(*mem));
+ } else
+ mem = kzalloc(sizeof(*mem), GFP_KERNEL);
+
+ if (!mem)
+ goto out;
+
+ if (statsize > PAGE_SIZE) {
+ cpustat = vmalloc(statsize);
+ if (!cpustat)
+ goto out_mem;
+ memset(cpustat, 0, statsize);
+ } else
+ cpustat = kzalloc(statsize, GFP_KERNEL);
+
+ if (!cpustat)
+ goto out_mem;
+
+ mem->stat.cpustat = cpustat;
return mem;
+
+out_mem:
+ if (is_vmalloc_addr(mem))
+ vfree(mem);
+ else
+ kfree(mem);
+out:
+ return NULL;
}

static void mem_cgroup_free(struct mem_cgroup *mem)
{
- if (sizeof(*mem) < PAGE_SIZE)
- kfree(mem);
+ if (is_vmalloc_addr(mem->stat.cpustat))
+ vfree(mem->stat.cpustat);
else
+ kfree(mem->stat.cpustat);
+
+ if (is_vmalloc_addr(mem))
vfree(mem);
+ else
+ kfree(mem);
}



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