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SubjectRe: [PATCH v3 1/7] Basic kernel memory functionality for the Memory Controller
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On Wed, Sep 21, 2011 at 7:53 AM, Glauber Costa <glommer@parallels.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@parallels.com>
>> CC: Paul Menage<paul@paulmenage.org>
>> CC: Greg Thelen<gthelen@google.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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