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Date: Thu, 22 Sep 2011 08:47:28 +0530
From: Balbir Singh <bsingharora@...il.com>
To: Glauber Costa <glommer@...allels.com>
Cc: linux-kernel@...r.kernel.org, paul@...lmenage.org,
lizf@...fujitsu.com, kamezawa.hiroyu@...fujitsu.com,
ebiederm@...ssion.com, davem@...emloft.net, gthelen@...gle.com,
netdev@...r.kernel.org, linux-mm@...ck.org, kirill@...temov.name,
Ying Han <yinghan@...gle.com>
Subject: Re: [PATCH v3 1/7] Basic kernel memory functionality for the Memory Controller
On Wed, Sep 21, 2011 at 7:53 AM, Glauber Costa <glommer@...allels.com> wrote:
>
> Hi people,
>
> Any insights on this series?
> Kame, is it inline with your expectations ?
>
> Thank you all
>
> On 09/18/2011 09:56 PM, Glauber Costa wrote:
>>
>> This patch lays down the foundation for the kernel memory component
>> of the Memory Controller.
>>
>> As of today, I am only laying down the following files:
>>
>> * memory.independent_kmem_limit
>> * memory.kmem.limit_in_bytes (currently ignored)
>> * memory.kmem.usage_in_bytes (always zero)
>>
>> Signed-off-by: Glauber Costa<glommer@...allels.com>
>> CC: Paul Menage<paul@...lmenage.org>
>> CC: Greg Thelen<gthelen@...gle.com>
>> ---
>> Documentation/cgroups/memory.txt | 30 +++++++++-
>> init/Kconfig | 11 ++++
>> mm/memcontrol.c | 115 ++++++++++++++++++++++++++++++++++++--
>> 3 files changed, 148 insertions(+), 8 deletions(-)
>>
>> diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
>> index 6f3c598..6f1954a 100644
>> --- a/Documentation/cgroups/memory.txt
>> +++ b/Documentation/cgroups/memory.txt
>> @@ -44,8 +44,9 @@ Features:
>> - oom-killer disable knob and oom-notifier
>> - Root cgroup has no limit controls.
>>
>> - Kernel memory and Hugepages are not under control yet. We just manage
>> - pages on LRU. To add more controls, we have to take care of performance.
>> + Hugepages is not under control yet. We just manage pages on LRU. To add more
>> + controls, we have to take care of performance. Kernel memory support is work
>> + in progress, and the current version provides basically functionality.
>>
>> Brief summary of control files.
>>
>> @@ -56,8 +57,11 @@ Brief summary of control files.
>> (See 5.5 for details)
>> memory.memsw.usage_in_bytes # show current res_counter usage for memory+Swap
>> (See 5.5 for details)
>> + memory.kmem.usage_in_bytes # show current res_counter usage for kmem only.
>> + (See 2.7 for details)
>> memory.limit_in_bytes # set/show limit of memory usage
>> memory.memsw.limit_in_bytes # set/show limit of memory+Swap usage
>> + memory.kmem.limit_in_bytes # if allowed, set/show limit of kernel memory
>> memory.failcnt # show the number of memory usage hits limits
>> memory.memsw.failcnt # show the number of memory+Swap hits limits
>> memory.max_usage_in_bytes # show max memory usage recorded
>> @@ -72,6 +76,9 @@ Brief summary of control files.
>> memory.oom_control # set/show oom controls.
>> memory.numa_stat # show the number of memory usage per numa node
>>
>> + memory.independent_kmem_limit # select whether or not kernel memory limits are
>> + independent of user limits
>> +
>> 1. History
>>
>> The memory controller has a long history. A request for comments for the memory
>> @@ -255,6 +262,25 @@ When oom event notifier is registered, event will be delivered.
>> per-zone-per-cgroup LRU (cgroup's private LRU) is just guarded by
>> zone->lru_lock, it has no lock of its own.
>>
>> +2.7 Kernel Memory Extension (CONFIG_CGROUP_MEM_RES_CTLR_KMEM)
>> +
>> + With the Kernel memory extension, the Memory Controller is able to limit
>> +the amount of kernel memory used by the system. Kernel memory is fundamentally
>> +different than user memory, since it can't be swapped out, which makes it
>> +possible to DoS the system by consuming too much of this precious resource.
>> +Kernel memory limits are not imposed for the root cgroup.
>> +
>> +Memory limits as specified by the standard Memory Controller may or may not
>> +take kernel memory into consideration. This is achieved through the file
>> +memory.independent_kmem_limit. A Value different than 0 will allow for kernel
>> +memory to be controlled separately.
>> +
>> +When kernel memory limits are not independent, the limit values set in
>> +memory.kmem files are ignored.
>> +
>> +Currently no soft limit is implemented for kernel memory. It is future work
>> +to trigger slab reclaim when those limits are reached.
>> +
Ying Han was also looking into this (cc'ing her)
>> 3. User Interface
>>
>> 0. Configuration
>> diff --git a/init/Kconfig b/init/Kconfig
>> index d627783..49e5839 100644
>> --- a/init/Kconfig
>> +++ b/init/Kconfig
>> @@ -689,6 +689,17 @@ config CGROUP_MEM_RES_CTLR_SWAP_ENABLED
>> For those who want to have the feature enabled by default should
>> select this option (if, for some reason, they need to disable it
>> then swapaccount=0 does the trick).
>> +config CGROUP_MEM_RES_CTLR_KMEM
>> + bool "Memory Resource Controller Kernel Memory accounting"
>> + depends on CGROUP_MEM_RES_CTLR
>> + default y
>> + help
>> + The Kernel Memory extension for Memory Resource Controller can limit
>> + the amount of memory used by kernel objects in the system. Those are
>> + fundamentally different from the entities handled by the standard
>> + Memory Controller, which are page-based, and can be swapped. Users of
>> + the kmem extension can use it to guarantee that no group of processes
>> + will ever exhaust kernel resources alone.
>>
>> config CGROUP_PERF
>> bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index ebd1e86..d32e931 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -73,7 +73,11 @@ static int really_do_swap_account __initdata = 0;
>> #define do_swap_account (0)
>> #endif
>>
>> -
>> +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
>> +int do_kmem_account __read_mostly = 1;
>> +#else
>> +#define do_kmem_account 0
>> +#endif
>> /*
>> * Statistics for memory cgroup.
>> */
>> @@ -270,6 +274,10 @@ struct mem_cgroup {
>> */
>> struct res_counter memsw;
>> /*
>> + * the counter to account for kmem usage.
>> + */
>> + struct res_counter kmem;
>> + /*
>> * Per cgroup active and inactive list, similar to the
>> * per zone LRU lists.
>> */
>> @@ -321,6 +329,11 @@ struct mem_cgroup {
>> */
>> unsigned long move_charge_at_immigrate;
>> /*
>> + * Should kernel memory limits be stabilished independently
>> + * from user memory ?
>> + */
>> + int kmem_independent;
>> + /*
>> * percpu counter.
>> */
>> struct mem_cgroup_stat_cpu *stat;
>> @@ -388,9 +401,14 @@ enum charge_type {
>> };
>>
>> /* for encoding cft->private value on file */
>> -#define _MEM (0)
>> -#define _MEMSWAP (1)
>> -#define _OOM_TYPE (2)
>> +
>> +enum mem_type {
>> + _MEM = 0,
>> + _MEMSWAP,
>> + _OOM_TYPE,
>> + _KMEM,
>> +};
>> +
>> #define MEMFILE_PRIVATE(x, val) (((x)<< 16) | (val))
>> #define MEMFILE_TYPE(val) (((val)>> 16)& 0xffff)
>> #define MEMFILE_ATTR(val) ((val)& 0xffff)
>> @@ -3943,10 +3961,15 @@ static inline u64 mem_cgroup_usage(struct mem_cgroup *mem, bool swap)
>> u64 val;
>>
>> if (!mem_cgroup_is_root(mem)) {
>> + val = 0;
>> + if (!mem->kmem_independent)
>> + val = res_counter_read_u64(&mem->kmem, RES_USAGE);
>> if (!swap)
>> - return res_counter_read_u64(&mem->res, RES_USAGE);
>> + val += res_counter_read_u64(&mem->res, RES_USAGE);
>> else
>> - return res_counter_read_u64(&mem->memsw, RES_USAGE);
>> + val += res_counter_read_u64(&mem->memsw, RES_USAGE);
>> +
>> + return val;
>> }
>>
>> val = mem_cgroup_recursive_stat(mem, MEM_CGROUP_STAT_CACHE);
>> @@ -3979,6 +4002,10 @@ static u64 mem_cgroup_read(struct cgroup *cont, struct cftype *cft)
>> else
>> val = res_counter_read_u64(&mem->memsw, name);
>> break;
>> + case _KMEM:
>> + val = res_counter_read_u64(&mem->kmem, name);
>> + break;
>> +
>> default:
>> BUG();
>> break;
>> @@ -4756,6 +4783,21 @@ static int mem_cgroup_reset_vmscan_stat(struct cgroup *cgrp,
>> return 0;
>> }
>>
>> +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
>> +static u64 kmem_limit_independent_read(struct cgroup *cont, struct cftype *cft)
>> +{
>> + return mem_cgroup_from_cont(cont)->kmem_independent;
>> +}
>> +
>> +static int kmem_limit_independent_write(struct cgroup *cont, struct cftype *cft,
>> + u64 val)
>> +{
>> + cgroup_lock();
>> + mem_cgroup_from_cont(cont)->kmem_independent = !!val;
>> + cgroup_unlock();
>> + return 0;
>> +}
I know we have a lot of pending xxx_from_cont() and struct cgroup
*cont, can we move it to memcg notation to be more consistent with our
usage. There is a patch to convert old usage
>> +#endif
>>
>> static struct cftype mem_cgroup_files[] = {
>> {
>> @@ -4877,6 +4919,47 @@ static int register_memsw_files(struct cgroup *cont, struct cgroup_subsys *ss)
>> }
>> #endif
>>
>> +
>> +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
>> +static struct cftype kmem_cgroup_files[] = {
>> + {
>> + .name = "independent_kmem_limit",
>> + .read_u64 = kmem_limit_independent_read,
>> + .write_u64 = kmem_limit_independent_write,
>> + },
>> + {
>> + .name = "kmem.usage_in_bytes",
>> + .private = MEMFILE_PRIVATE(_KMEM, RES_USAGE),
>> + .read_u64 = mem_cgroup_read,
>> + },
>> + {
>> + .name = "kmem.limit_in_bytes",
>> + .private = MEMFILE_PRIVATE(_KMEM, RES_LIMIT),
>> + .read_u64 = mem_cgroup_read,
>> + },
>> +};
>> +
>> +static int register_kmem_files(struct cgroup *cont, struct cgroup_subsys *ss)
>> +{
>> + struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
>> + int ret = 0;
>> +
>> + if (!do_kmem_account)
>> + return 0;
>> +
>> + if (!mem_cgroup_is_root(mem))
>> + ret = cgroup_add_files(cont, ss, kmem_cgroup_files,
>> + ARRAY_SIZE(kmem_cgroup_files));
>> + return ret;
>> +};
>> +
>> +#else
>> +static int register_kmem_files(struct cgroup *cont, struct cgroup_subsys *ss)
>> +{
>> + return 0;
>> +}
>> +#endif
>> +
>> static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
>> {
>> struct mem_cgroup_per_node *pn;
>> @@ -5075,6 +5158,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
>> if (parent&& parent->use_hierarchy) {
>> res_counter_init(&mem->res,&parent->res);
>> res_counter_init(&mem->memsw,&parent->memsw);
>> + res_counter_init(&mem->kmem,&parent->kmem);
>> /*
>> * We increment refcnt of the parent to ensure that we can
>> * safely access it on res_counter_charge/uncharge.
>> @@ -5085,6 +5169,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
>> } else {
>> res_counter_init(&mem->res, NULL);
>> res_counter_init(&mem->memsw, NULL);
>> + res_counter_init(&mem->kmem, NULL);
>> }
>> mem->last_scanned_child = 0;
>> mem->last_scanned_node = MAX_NUMNODES;
>> @@ -5129,6 +5214,10 @@ static int mem_cgroup_populate(struct cgroup_subsys *ss,
>>
>> if (!ret)
>> ret = register_memsw_files(cont, ss);
>> +
>> + if (!ret)
>> + ret = register_kmem_files(cont, ss);
>> +
>> return ret;
>> }
>>
>> @@ -5665,3 +5754,17 @@ static int __init enable_swap_account(char *s)
>> __setup("swapaccount=", enable_swap_account);
>>
>> #endif
>> +
>> +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
>> +static int __init disable_kmem_account(char *s)
>> +{
>> + /* consider enabled if no parameter or 1 is given */
>> + if (!strcmp(s, "1"))
>> + do_kmem_account = 1;
>> + else if (!strcmp(s, "0"))
>> + do_kmem_account = 0;
>> + return 1;
>> +}
>> +__setup("kmemaccount=", disable_kmem_account);
>> +
>> +#endif
The infrastructure looks OK, we need better integration with
statistics for kmem usage.
Balbir Singh
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