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memcg: add per-memcg total kernel memory stat

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Currently memcg stats show several types of kernel memory: kernel stack,
page tables, sock, vmalloc, and slab.  However, there are other
allocations with __GFP_ACCOUNT (or supersets such as GFP_KERNEL_ACCOUNT)
that are not accounted in any of those stats, a few examples are:

 - various kvm allocations (e.g. allocated pages to create vcpus)
 - io_uring
 - tmp_page in pipes during pipe_write()
 - bpf ringbuffers
 - unix sockets

Keeping track of the total kernel memory is essential for the ease of
migration from cgroup v1 to v2 as there are large discrepancies between
v1's kmem.usage_in_bytes and the sum of the available kernel memory
stats in v2.  Adding separate memcg stats for all __GFP_ACCOUNT kernel
allocations is an impractical maintenance burden as there a lot of those
all over the kernel code, with more use cases likely to show up in the
future.

Therefore, add a "kernel" memcg stat that is analogous to kmem page
counter, with added benefits such as using rstat infrastructure which
aggregates stats more efficiently.  Additionally, this provides a
lighter alternative in case the legacy kmem is deprecated in the future

[yosryahmed@google.com: v2]
  Link: https://lkml.kernel.org/r/20220203193856.972500-1-yosryahmed@google.com

Link: https://lkml.kernel.org/r/20220201200823.3283171-1-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Yosry Ahmed 2022-03-22 14:40:10 -07:00 committed by Linus Torvalds
parent 086f694a75
commit a8c49af3be
3 changed files with 27 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
Documentation/admin-guide/cgroup-v2.rst
View File

@ -1301,6 +1301,11 @@ PAGE_SIZE multiple when read back.
Amount of memory used to cache filesystem data,
including tmpfs and shared memory.
kernel (npn)
Amount of total kernel memory, including
(kernel_stack, pagetables, percpu, vmalloc, slab) in
addition to other kernel memory use cases.
kernel_stack
Amount of memory allocated to kernel stacks.

1
include/linux/memcontrol.h
View File

@ -34,6 +34,7 @@ enum memcg_stat_item {
MEMCG_SOCK,
MEMCG_PERCPU_B,
MEMCG_VMALLOC,
MEMCG_KMEM,
MEMCG_NR_STAT,
};

27
mm/memcontrol.c
View File

@ -1371,6 +1371,7 @@ struct memory_stat {
static const struct memory_stat memory_stats[] = {
{ "anon", NR_ANON_MAPPED },
{ "file", NR_FILE_PAGES },
{ "kernel", MEMCG_KMEM },
{ "kernel_stack", NR_KERNEL_STACK_KB },
{ "pagetables", NR_PAGETABLE },
{ "percpu", MEMCG_PERCPU_B },
@ -2114,6 +2115,7 @@ static DEFINE_MUTEX(percpu_charge_mutex);
static void drain_obj_stock(struct obj_stock *stock);
static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
struct mem_cgroup *root_memcg);
static void memcg_account_kmem(struct mem_cgroup *memcg, int nr_pages);
#else
static inline void drain_obj_stock(struct obj_stock *stock)
@ -2124,6 +2126,9 @@ static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
{
return false;
}
static void memcg_account_kmem(struct mem_cgroup *memcg, int nr_pages)
{
}
#endif
/**
@ -2979,6 +2984,18 @@ static void memcg_free_cache_id(int id)
ida_simple_remove(&memcg_cache_ida, id);
}
static void memcg_account_kmem(struct mem_cgroup *memcg, int nr_pages)
{
mod_memcg_state(memcg, MEMCG_KMEM, nr_pages);
if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
if (nr_pages > 0)
page_counter_charge(&memcg->kmem, nr_pages);
else
page_counter_uncharge(&memcg->kmem, -nr_pages);
}
}
/*
* obj_cgroup_uncharge_pages: uncharge a number of kernel pages from a objcg
* @objcg: object cgroup to uncharge
@ -2991,8 +3008,7 @@ static void obj_cgroup_uncharge_pages(struct obj_cgroup *objcg,
memcg = get_mem_cgroup_from_objcg(objcg);
if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
page_counter_uncharge(&memcg->kmem, nr_pages);
memcg_account_kmem(memcg, -nr_pages);
refill_stock(memcg, nr_pages);
css_put(&memcg->css);
@ -3018,8 +3034,7 @@ static int obj_cgroup_charge_pages(struct obj_cgroup *objcg, gfp_t gfp,
if (ret)
goto out;
if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
page_counter_charge(&memcg->kmem, nr_pages);
memcg_account_kmem(memcg, nr_pages);
out:
css_put(&memcg->css);
@ -6801,8 +6816,8 @@ static void uncharge_batch(const struct uncharge_gather *ug)
page_counter_uncharge(&ug->memcg->memory, ug->nr_memory);
if (do_memsw_account())
page_counter_uncharge(&ug->memcg->memsw, ug->nr_memory);
if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && ug->nr_kmem)
page_counter_uncharge(&ug->memcg->kmem, ug->nr_kmem);
if (ug->nr_kmem)
memcg_account_kmem(ug->memcg, -ug->nr_kmem);
memcg_oom_recover(ug->memcg);
}