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Message-ID: <20241211203951.764733-3-joshua.hahnjy@gmail.com>
Date: Wed, 11 Dec 2024 12:39:50 -0800
From: Joshua Hahn <joshua.hahnjy@...il.com>
To: shakeel.butt@...ux.dev
Cc: hannes@...xchg.org,
mhocko@...nel.org,
roman.gushchin@...ux.dev,
muchun.song@...ux.dev,
akpm@...ux-foundation.org,
sj@...nel.org,
cgroups@...r.kernel.org,
linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
kernel-team@...a.com
Subject: [v3 PATCH 2/3] memcg/hugetlb: Introduce mem_cgroup_charge_hugetlb
This patch introduces mem_cgroup_charge_hugetlb which combines the logic
of mem_cgroup_hugetlb_try_charge / mem_cgroup_hugetlb_commit_charge and
removes the need for mem_cgroup_hugetlb_cancel_charge. It also reduces
the footprint of memcg in hugetlb code and consolidates all memcg
related error paths into one.
Signed-off-by: Joshua Hahn <joshua.hahnjy@...il.com>
---
include/linux/memcontrol.h | 7 +++++++
mm/hugetlb.c | 35 ++++++++++++++---------------------
mm/memcontrol.c | 34 ++++++++++++++++++++++++++++++++++
3 files changed, 55 insertions(+), 21 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 5502aa8e138e..f4271cfdba92 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -649,6 +649,8 @@ static inline int mem_cgroup_charge(struct folio *folio, struct mm_struct *mm,
int mem_cgroup_hugetlb_try_charge(struct mem_cgroup *memcg, gfp_t gfp,
long nr_pages);
+int mem_cgroup_charge_hugetlb(struct folio* folio, gfp_t gfp);
+
int mem_cgroup_swapin_charge_folio(struct folio *folio, struct mm_struct *mm,
gfp_t gfp, swp_entry_t entry);
@@ -1152,6 +1154,11 @@ static inline int mem_cgroup_hugetlb_try_charge(struct mem_cgroup *memcg,
return 0;
}
+static inline int mem_cgroup_charge_hugetlb(struct folio* folio, gfp_t gfp)
+{
+ return 0;
+}
+
static inline int mem_cgroup_swapin_charge_folio(struct folio *folio,
struct mm_struct *mm, gfp_t gfp, swp_entry_t entry)
{
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index ea2ed8e301ef..f0f0ffae30a3 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2967,21 +2967,13 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma,
struct hugepage_subpool *spool = subpool_vma(vma);
struct hstate *h = hstate_vma(vma);
struct folio *folio;
- long map_chg, map_commit, nr_pages = pages_per_huge_page(h);
+ long map_chg, map_commit;
long gbl_chg;
- int memcg_charge_ret, ret, idx;
+ int 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);
/*
* Examine the region/reserve map to determine if the process
@@ -2989,12 +2981,8 @@ 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 (!memcg_charge_ret)
- mem_cgroup_cancel_charge(memcg, nr_pages);
- mem_cgroup_put(memcg);
+ if (map_chg < 0)
return ERR_PTR(-ENOMEM);
- }
/*
* Processes that did not create the mapping will have no
@@ -3092,10 +3080,18 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma,
}
}
- if (!memcg_charge_ret)
- mem_cgroup_commit_charge(folio, memcg);
+ ret = mem_cgroup_charge_hugetlb(folio, gfp);
+ /*
+ * Unconditionally increment NR_HUGETLB here. If it turns out that
+ * mem_cgroup_charge_hugetlb failed, then immediately free the page and
+ * decrement NR_HUGETLB.
+ */
lruvec_stat_mod_folio(folio, NR_HUGETLB, pages_per_huge_page(h));
- mem_cgroup_put(memcg);
+
+ if (ret == -ENOMEM) {
+ free_huge_folio(folio);
+ return ERR_PTR(-ENOMEM);
+ }
return folio;
@@ -3110,9 +3106,6 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma,
hugepage_subpool_put_pages(spool, 1);
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);
}
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b25eab9c933e..c903e260a830 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4561,6 +4561,40 @@ int mem_cgroup_hugetlb_try_charge(struct mem_cgroup *memcg, gfp_t gfp,
return 0;
}
+/**
+ * mem_cgroup_charge_hugetlb - charge the memcg for a hugetlb folio
+ * @folio: folio being charged
+ * @gfp: reclaim mode
+ *
+ * This function is called when allocating a huge page folio, after the page has
+ * already been obtained and charged to the appropriate hugetlb cgroup
+ * controller (if it is enabled).
+ *
+ * Returns ENOMEM if the memcg is already full.
+ * Returns 0 if either the charge was successful, or if we skip the charging.
+ */
+int mem_cgroup_charge_hugetlb(struct folio *folio, gfp_t gfp)
+{
+ struct mem_cgroup *memcg = get_mem_cgroup_from_current();
+ int ret = 0;
+
+ /*
+ * Even memcg does not account for hugetlb, we still want to update
+ * system-level stats via lruvec_stat_mod_folio. Return 0, and skip
+ * charging the memcg.
+ */
+ if (mem_cgroup_disabled() || !memcg_accounts_hugetlb() ||
+ !memcg || !cgroup_subsys_on_dfl(memory_cgrp_subsys))
+ goto out;
+
+ if (charge_memcg(folio, memcg, gfp))
+ ret = -ENOMEM;
+
+out:
+ mem_cgroup_put(memcg);
+ return ret;
+}
+
/**
* mem_cgroup_swapin_charge_folio - Charge a newly allocated folio for swapin.
* @folio: folio to charge.
--
2.43.5
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