Commit d151025a authored by Nhat Pham's avatar Nhat Pham Committed by Chen Ridong
Browse files

hugetlb: memcg: account hugetlb-backed memory in memory controller 

mainline inclusion
from mainline-v6.7-rc1
commit 8cba9576df601c384abd334a503c3f6e1e29eefb
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I91HYH

----------------------------------------------------------------------

Currently, hugetlb memory usage is not acounted for in the memory
controller, which could lead to memory overprotection for cgroups with
hugetlb-backed memory.  This has been observed in our production system.

For instance, here is one of our usecases: suppose there are two 32G
containers.  The machine is booted with hugetlb_cma=6G, and each container
may or may not use up to 3 gigantic page, depending on the workload within
it.  The rest is anon, cache, slab, etc.  We can set the hugetlb cgroup
limit of each cgroup to 3G to enforce hugetlb fairness.  But it is very
difficult to configure memory.max to keep overall consumption, including
anon, cache, slab etc.  fair.

What we have had to resort to is to constantly poll hugetlb usage and
readjust memory.max.  Similar procedure is done to other memory limits
(memory.low for e.g).  However, this is rather cumbersome and buggy.
Furthermore, when there is a delay in memory limits correction, (for e.g
when hugetlb usage changes within consecutive runs of the userspace
agent), the system could be in an over/underprotected state.

This patch rectifies this issue by charging the memcg when the hugetlb
folio is utilized, and uncharging when the folio is freed (analogous to
the hugetlb controller).  Note that we do not charge when the folio is
allocated to the hugetlb pool, because at this point it is not owned by
any memcg.

Some caveats to consider:
  * This feature is only available on cgroup v2.
  * There is no hugetlb pool management involved in the memory
    controller. As stated above, hugetlb folios are only charged towards
    the memory controller when it is used. Host overcommit management
    has to consider it when configuring hard limits.
  * Failure to charge towards the memcg results in SIGBUS. This could
    happen even if the hugetlb pool still has pages (but the cgroup
    limit is hit and reclaim attempt fails).
  * When this feature is enabled, hugetlb pages contribute to memory
    reclaim protection. low, min limits tuning must take into account
    hugetlb memory.
  * Hugetlb pages utilized while this option is not selected will not
    be tracked by the memory controller (even if cgroup v2 is remounted
    later on).

Link: https://lkml.kernel.org/r/20231006184629.155543-4-nphamcs@gmail.com


Signed-off-by: default avatarNhat Pham <nphamcs@gmail.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Cc: Frank van der Linden <fvdl@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Rik van Riel <riel@surriel.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Tejun heo <tj@kernel.org>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Conflict:
            mm/hugetlb.c
Signed-off-by: default avatarChen Ridong <chenridong@huawei.com>
parent cd0b9cc1

Documentation/admin-guide/cgroup-v2.rst

+29 −0
Original line number Diff line number Diff line
@@ -210,6 +210,35 @@ cgroup v2 currently supports the following mount options. 
        relying on the original semantics (e.g. specifying bogusly

        high 'bypass' protection values at higher tree levels).



  memory_hugetlb_accounting

        Count HugeTLB memory usage towards the cgroup's overall

        memory usage for the memory controller (for the purpose of

        statistics reporting and memory protetion). This is a new

        behavior that could regress existing setups, so it must be

        explicitly opted in with this mount option.



        A few caveats to keep in mind:



        * There is no HugeTLB pool management involved in the memory

          controller. The pre-allocated pool does not belong to anyone.

          Specifically, when a new HugeTLB folio is allocated to

          the pool, it is not accounted for from the perspective of the

          memory controller. It is only charged to a cgroup when it is

          actually used (for e.g at page fault time). Host memory

          overcommit management has to consider this when configuring

          hard limits. In general, HugeTLB pool management should be

          done via other mechanisms (such as the HugeTLB controller).

        * Failure to charge a HugeTLB folio to the memory controller

          results in SIGBUS. This could happen even if the HugeTLB pool

          still has pages available (but the cgroup limit is hit and

          reclaim attempt fails).

        * Charging HugeTLB memory towards the memory controller affects

          memory protection and reclaim dynamics. Any userspace tuning

          (of low, min limits for e.g) needs to take this into account.

        * HugeTLB pages utilized while this option is not selected

          will not be tracked by the memory controller (even if cgroup

          v2 is remounted later on).





Organizing Processes and Threads

--------------------------------

include/linux/cgroup-defs.h

+5 −0
Original line number Diff line number Diff line
@@ -116,6 +116,11 @@ enum { 
	 * Enable recursive subtree protection

	 */

	CGRP_ROOT_MEMORY_RECURSIVE_PROT = (1 << 18),



	/*

	 * Enable hugetlb accounting for the memory controller.

	 */

	 CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING = (1 << 19),

};



/* cftype->flags */

include/linux/memcontrol.h

+9 −0
Original line number Diff line number Diff line
@@ -807,6 +807,9 @@ static inline int mem_cgroup_charge(struct folio *folio, struct mm_struct *mm, 
	return __mem_cgroup_charge(folio, mm, gfp);

}



int mem_cgroup_hugetlb_try_charge(struct mem_cgroup *memcg, gfp_t gfp,

		long nr_pages);



int mem_cgroup_swapin_charge_folio(struct folio *folio, struct mm_struct *mm,

				  gfp_t gfp, swp_entry_t entry);

void mem_cgroup_swapin_uncharge_swap(swp_entry_t entry);
@@ -1407,6 +1410,12 @@ static inline int mem_cgroup_charge(struct folio *folio, 
	return 0;

}



static inline int mem_cgroup_hugetlb_try_charge(struct mem_cgroup *memcg,

		gfp_t gfp, long nr_pages)

{

	return 0;

}



static inline int mem_cgroup_swapin_charge_folio(struct folio *folio,

			struct mm_struct *mm, gfp_t gfp, swp_entry_t entry)

{

kernel/cgroup/cgroup.c

+14 −1
Original line number Diff line number Diff line
@@ -1906,6 +1906,7 @@ enum cgroup2_param { 
	Opt_favordynmods,

	Opt_memory_localevents,

	Opt_memory_recursiveprot,

	Opt_memory_hugetlb_accounting,

	nr__cgroup2_params

};
@@ -1914,6 +1915,7 @@ static const struct fs_parameter_spec cgroup2_fs_parameters[] = { 
	fsparam_flag("favordynmods",		Opt_favordynmods),

	fsparam_flag("memory_localevents",	Opt_memory_localevents),

	fsparam_flag("memory_recursiveprot",	Opt_memory_recursiveprot),

	fsparam_flag("memory_hugetlb_accounting", Opt_memory_hugetlb_accounting),

	{}

};
@@ -1940,6 +1942,9 @@ static int cgroup2_parse_param(struct fs_context *fc, struct fs_parameter *param 
	case Opt_memory_recursiveprot:

		ctx->flags |= CGRP_ROOT_MEMORY_RECURSIVE_PROT;

		return 0;

	case Opt_memory_hugetlb_accounting:

		ctx->flags |= CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;

		return 0;

	}

	return -EINVAL;

}
@@ -1964,6 +1969,11 @@ static void apply_cgroup_root_flags(unsigned int root_flags) 
			cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_RECURSIVE_PROT;

		else

			cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_RECURSIVE_PROT;



		if (root_flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING)

			cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;

		else

			cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;

	}

}
@@ -1977,6 +1987,8 @@ static int cgroup_show_options(struct seq_file *seq, struct kernfs_root *kf_root 
		seq_puts(seq, ",memory_localevents");

	if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_RECURSIVE_PROT)

		seq_puts(seq, ",memory_recursiveprot");

	if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING)

		seq_puts(seq, ",memory_hugetlb_accounting");

	return 0;

}
@@ -7163,7 +7175,8 @@ static ssize_t features_show(struct kobject *kobj, struct kobj_attribute *attr, 
			"nsdelegate\n"

			"favordynmods\n"

			"memory_localevents\n"

			"memory_recursiveprot\n");

			"memory_recursiveprot\n"

			"memory_hugetlb_accounting\n");

}

static struct kobj_attribute cgroup_features_attr = __ATTR_RO(features);

mm/hugetlb.c

+28 −8
Original line number Diff line number Diff line
@@ -1947,7 +1947,7 @@ void free_huge_folio(struct folio *folio) 
				     pages_per_huge_page(h), folio);

	hugetlb_cgroup_uncharge_folio_rsvd(hstate_index(h),

					  pages_per_huge_page(h), folio);



	mem_cgroup_uncharge(folio);

	if (page_from_dynamic_pool(folio_page(folio, 0))) {

		list_del(&folio->lru);

		spin_unlock_irqrestore(&hugetlb_lock, flags);
@@ -3144,11 +3144,20 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, 
	struct hugetlbfs_inode_info *info = HUGETLBFS_I(file_inode(vma->vm_file));

	struct hstate *h = hstate_vma(vma);

	struct folio *folio;

	long map_chg, map_commit;

	long map_chg, map_commit, nr_pages = pages_per_huge_page(h);

	long gbl_chg;

	int ret, idx;

	int memcg_charge_ret, ret, idx;

	struct hugetlb_cgroup *h_cg = NULL;

	struct mem_cgroup *memcg;

	bool deferred_reserve;

	gfp_t gfp = htlb_alloc_mask(h) | __GFP_RETRY_MAYFAIL;



	memcg = get_mem_cgroup_from_current();

	memcg_charge_ret = mem_cgroup_hugetlb_try_charge(memcg, gfp, nr_pages);

	if (memcg_charge_ret == -ENOMEM) {

		mem_cgroup_put(memcg);

		return ERR_PTR(-ENOMEM);

	}



	idx = hstate_index(h);

	/*
@@ -3157,8 +3166,12 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, 
	 * code of zero indicates a reservation exists (no change).

	 */

	map_chg = gbl_chg = vma_needs_reservation(h, vma, addr);

	if (map_chg < 0)

	if (map_chg < 0) {

		if (!memcg_charge_ret)

			mem_cgroup_cancel_charge(memcg, nr_pages);

		mem_cgroup_put(memcg);

		return ERR_PTR(-ENOMEM);

	}



	/*

	 * Processes that did not create the mapping will have no
@@ -3169,10 +3182,8 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, 
	 */

	if (map_chg || avoid_reserve) {

		gbl_chg = hugepage_subpool_get_pages(spool, 1, info);

		if (gbl_chg < 0) {

			vma_end_reservation(h, vma, addr);

			return ERR_PTR(-ENOSPC);

		}

		if (gbl_chg < 0)

			goto out_end_reservation;



		/*

		 * Even though there was no reservation in the region/reserve
@@ -3268,6 +3279,11 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, 
			hugetlb_cgroup_uncharge_folio_rsvd(hstate_index(h),

					pages_per_huge_page(h), folio);

	}



	if (!memcg_charge_ret)

		mem_cgroup_commit_charge(folio, memcg);

	mem_cgroup_put(memcg);



	return folio;



out_uncharge_cgroup:
@@ -3279,7 +3295,11 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, 
out_subpool_put:

	if (map_chg || avoid_reserve)

		hugepage_subpool_put_pages(spool, 1, info);

out_end_reservation:

	vma_end_reservation(h, vma, addr);

	if (!memcg_charge_ret)

		mem_cgroup_cancel_charge(memcg, nr_pages);

	mem_cgroup_put(memcg);

	return ERR_PTR(-ENOSPC);

}