Re: [PATCH 13/14] mm: memcontrol: account socket memory in unified hierarchy memory controller

Johannes Weiner
2015-11-16T18:18:22Z

On Mon, Nov 16, 2015 at 04:59:25PM +0100, Michal Hocko wrote:
> On Thu 12-11-15 18:41:32, Johannes Weiner wrote:
> > Socket memory can be a significant share of overall memory consumed by
> > common workloads. In order to provide reasonable resource isolation in
> > the unified hierarchy, this type of memory needs to be included in the
> > tracking/accounting of a cgroup under active memory resource control.
> >
> > Overhead is only incurred when a non-root control group is created AND
> > the memory controller is instructed to track and account the memory
> > footprint of that group. cgroup.memory=nosocket can be specified on
> > the boot commandline to override any runtime configuration and
> > forcibly exclude socket memory from active memory resource control.
>
> Do you have any numbers about the overhead?

Hm? Performance numbers make sense when you have a specific scenario
and a theory on how to optimize the implementation for it. What load
would you test and what would be the baseline to compare it to?

> > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
>
> With a way to disable this feature I am OK with it.
> cgroup.memory=nosocket should be documented (at least in
> Documentation/kernel-parameters.txt)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index f8aae63..d518340 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -599,6 +599,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
cut the overhead, others just disable the usage. So
only cgroup_disable=memory is actually worthy}

+ cgroup.memory= [KNL] Pass options to the cgroup memory controller.
+ Format: <string>
+ nosocket -- Disable socket memory accounting.
+
checkreqprot [SELINUX] Set initial checkreqprot flag value.
Format: { "0" | "1" }
See security/selinux/Kconfig help text.

> Other than that
> Acked-by: Michal Hocko <mhocko@suse.com>

Thanks!

---
>From abe0670cec1424a5b4f43dfabff8bb27a1007ced Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@cmpxchg.org>
Date: Wed, 14 Oct 2015 22:25:20 -0700
Subject: [PATCH] mm: memcontrol: account socket memory in unified hierarchy
memory controller

Socket memory can be a significant share of overall memory consumed by
common workloads. In order to provide reasonable resource isolation in
the unified hierarchy, this type of memory needs to be included in the
tracking/accounting of a cgroup under active memory resource control.

Overhead is only incurred when a non-root control group is created AND
the memory controller is instructed to track and account the memory
footprint of that group. cgroup.memory=nosocket can be specified on
the boot commandline to override any runtime configuration and
forcibly exclude socket memory from active memory resource control.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
---
Documentation/kernel-parameters.txt | 4 ++
include/linux/memcontrol.h | 12 +++-
mm/memcontrol.c | 131 +++++++++++++++++++++++++++++-------
3 files changed, 122 insertions(+), 25 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index f8aae63..d518340 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -599,6 +599,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
cut the overhead, others just disable the usage. So
only cgroup_disable=memory is actually worthy}

+ cgroup.memory= [KNL] Pass options to the cgroup memory controller.
+ Format: <string>
+ nosocket -- Disable socket memory accounting.
+
checkreqprot [SELINUX] Set initial checkreqprot flag value.
Format: { "0" | "1" }
See security/selinux/Kconfig help text.
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 4cf5afa..809d6de 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -256,6 +256,10 @@ struct mem_cgroup {
struct wb_domain cgwb_domain;
#endif

+#ifdef CONFIG_INET
+ struct work_struct socket_work;
+#endif
+
/* List of events which userspace want to receive */
struct list_head event_list;
spinlock_t event_list_lock;
@@ -691,7 +695,7 @@ static inline void mem_cgroup_wb_stats(struct bdi_writeback *wb,

#endif /* CONFIG_CGROUP_WRITEBACK */

-#if defined(CONFIG_INET) && defined(CONFIG_MEMCG_KMEM)
+#ifdef CONFIG_INET
struct sock;
extern struct static_key memcg_sockets_enabled_key;
#define mem_cgroup_sockets_enabled static_key_false(&memcg_sockets_enabled_key)
@@ -701,11 +705,15 @@ bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages);
void mem_cgroup_uncharge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages);
static inline bool mem_cgroup_under_socket_pressure(struct mem_cgroup *memcg)
{
+#ifdef CONFIG_MEMCG_KMEM
return memcg->tcp_mem.memory_pressure;
+#else
+ return false;
+#endif
}
#else
#define mem_cgroup_sockets_enabled 0
-#endif /* CONFIG_INET && CONFIG_MEMCG_KMEM */
+#endif /* CONFIG_INET */

#ifdef CONFIG_MEMCG_KMEM
extern struct static_key memcg_kmem_enabled_key;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 408fb04..cad9525 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -80,6 +80,9 @@ struct mem_cgroup *root_mem_cgroup __read_mostly;

#define MEM_CGROUP_RECLAIM_RETRIES 5

+/* Socket memory accounting disabled? */
+static bool cgroup_memory_nosocket;
+
/* Whether the swap controller is active */
#ifdef CONFIG_MEMCG_SWAP
int do_swap_account __read_mostly;
@@ -1923,6 +1926,18 @@ static int memcg_cpu_hotplug_callback(struct notifier_block *nb,
return NOTIFY_OK;
}

+static void reclaim_high(struct mem_cgroup *memcg,
+ unsigned int nr_pages,
+ gfp_t gfp_mask)
+{
+ do {
+ if (page_counter_read(&memcg->memory) <= memcg->high)
+ continue;
+ mem_cgroup_events(memcg, MEMCG_HIGH, 1);
+ try_to_free_mem_cgroup_pages(memcg, nr_pages, gfp_mask, true);
+ } while ((memcg = parent_mem_cgroup(memcg)));
+}
+
/*
* Scheduled by try_charge() to be executed from the userland return path
* and reclaims memory over the high limit.
@@ -1930,20 +1945,13 @@ static int memcg_cpu_hotplug_callback(struct notifier_block *nb,
void mem_cgroup_handle_over_high(void)
{
unsigned int nr_pages = current->memcg_nr_pages_over_high;
- struct mem_cgroup *memcg, *pos;
+ struct mem_cgroup *memcg;

if (likely(!nr_pages))
return;

- pos = memcg = get_mem_cgroup_from_mm(current->mm);
-
- do {
- if (page_counter_read(&pos->memory) <= pos->high)
- continue;
- mem_cgroup_events(pos, MEMCG_HIGH, 1);
- try_to_free_mem_cgroup_pages(pos, nr_pages, GFP_KERNEL, true);
- } while ((pos = parent_mem_cgroup(pos)));
-
+ memcg = get_mem_cgroup_from_mm(current->mm);
+ reclaim_high(memcg, nr_pages, GFP_KERNEL);
css_put(&memcg->css);
current->memcg_nr_pages_over_high = 0;
}
@@ -4141,6 +4149,8 @@ struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg)
}
EXPORT_SYMBOL(parent_mem_cgroup);

+static void socket_work_func(struct work_struct *work);
+
static struct cgroup_subsys_state * __ref
mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
{
@@ -4180,6 +4190,9 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
#ifdef CONFIG_CGROUP_WRITEBACK
INIT_LIST_HEAD(&memcg->cgwb_list);
#endif
+#ifdef CONFIG_INET
+ INIT_WORK(&memcg->socket_work, socket_work_func);
+#endif
return &memcg->css;

free_out:
@@ -4237,6 +4250,11 @@ mem_cgroup_css_online(struct cgroup_subsys_state *css)
if (ret)
return ret;

+#ifdef CONFIG_INET
+ if (cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_nosocket)
+ static_key_slow_inc(&memcg_sockets_enabled_key);
+#endif
+
/*
* Make sure the memcg is initialized: mem_cgroup_iter()
* orders reading memcg->initialized against its callers
@@ -4276,6 +4294,11 @@ static void mem_cgroup_css_free(struct cgroup_subsys_state *css)
struct mem_cgroup *memcg = mem_cgroup_from_css(css);

memcg_destroy_kmem(memcg);
+#ifdef CONFIG_INET
+ if (cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_nosocket)
+ static_key_slow_dec(&memcg_sockets_enabled_key);
+ cancel_work_sync(&memcg->socket_work);
+#endif
__mem_cgroup_free(memcg);
}

@@ -5464,8 +5487,7 @@ void mem_cgroup_replace_page(struct page *oldpage, struct page *newpage)
commit_charge(newpage, memcg, true);
}

-/* Writing them here to avoid exposing memcg's inner layout */
-#if defined(CONFIG_INET) && defined(CONFIG_MEMCG_KMEM)
+#ifdef CONFIG_INET

struct static_key memcg_sockets_enabled_key;
EXPORT_SYMBOL(memcg_sockets_enabled_key);
@@ -5490,10 +5512,16 @@ void sock_update_memcg(struct sock *sk)

rcu_read_lock();
memcg = mem_cgroup_from_task(current);
- if (memcg != root_mem_cgroup &&
- test_bit(MEMCG_SOCK_ACTIVE, &memcg->tcp_mem.flags) &&
- css_tryget_online(&memcg->css))
+ if (memcg == root_mem_cgroup)
+ goto out;
+#ifdef CONFIG_MEMCG_KMEM
+ if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
+ !test_bit(MEMCG_SOCK_ACTIVE, &memcg->tcp_mem.flags))
+ goto out;
+#endif
+ if (css_tryget_online(&memcg->css))
sk->sk_memcg = memcg;
+out:
rcu_read_unlock();
}
EXPORT_SYMBOL(sock_update_memcg);
@@ -5504,6 +5532,14 @@ void sock_release_memcg(struct sock *sk)
css_put(&sk->sk_memcg->css);
}

+static void socket_work_func(struct work_struct *work)
+{
+ struct mem_cgroup *memcg;
+
+ memcg = container_of(work, struct mem_cgroup, socket_work);
+ reclaim_high(memcg, CHARGE_BATCH, GFP_KERNEL);
+}
+
/**
* mem_cgroup_charge_skmem - charge socket memory
* @memcg: memcg to charge
@@ -5514,16 +5550,43 @@ void sock_release_memcg(struct sock *sk)
*/
bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
{
+ unsigned int batch = max(CHARGE_BATCH, nr_pages);
struct page_counter *counter;
+ bool force = false;

- if (page_counter_try_charge(&memcg->tcp_mem.memory_allocated,
- nr_pages, &counter)) {
- memcg->tcp_mem.memory_pressure = 0;
+#ifdef CONFIG_MEMCG_KMEM
+ if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
+ if (page_counter_try_charge(&memcg->tcp_mem.memory_allocated,
+ nr_pages, &counter)) {
+ memcg->tcp_mem.memory_pressure = 0;
+ return true;
+ }
+ page_counter_charge(&memcg->tcp_mem.memory_allocated, nr_pages);
+ memcg->tcp_mem.memory_pressure = 1;
+ return false;
+ }
+#endif
+ if (consume_stock(memcg, nr_pages))
return true;
+retry:
+ if (page_counter_try_charge(&memcg->memory, batch, &counter))
+ goto done;
+
+ if (batch > nr_pages) {
+ batch = nr_pages;
+ goto retry;
}
- page_counter_charge(&memcg->tcp_mem.memory_allocated, nr_pages);
- memcg->tcp_mem.memory_pressure = 1;
- return false;
+
+ page_counter_charge(&memcg->memory, batch);
+ force = true;
+done:
+ css_get_many(&memcg->css, batch);
+ if (batch > nr_pages)
+ refill_stock(memcg, batch - nr_pages);
+
+ schedule_work(&memcg->socket_work);
+
+ return !force;
}

/**
@@ -5533,10 +5596,32 @@ bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
*/
void mem_cgroup_uncharge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
{
- page_counter_uncharge(&memcg->tcp_mem.memory_allocated, nr_pages);
+#ifdef CONFIG_MEMCG_KMEM
+ if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
+ page_counter_uncharge(&memcg->tcp_mem.memory_allocated,
+ nr_pages);
+ return;
+ }
+#endif
+ page_counter_uncharge(&memcg->memory, nr_pages);
+ css_put_many(&memcg->css, nr_pages);
}

-#endif
+#endif /* CONFIG_INET */
+
+static int __init cgroup_memory(char *s)
+{
+ char *token;
+
+ while ((token = strsep(&s, ",")) != NULL) {
+ if (!*token)
+ continue;
+ if (!strcmp(token, "nosocket"))
+ cgroup_memory_nosocket = true;
+ }
+ return 0;
+}
+__setup("cgroup.memory=", cgroup_memory);

/*
* subsys_initcall() for memory controller.
--
2.6.2