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cgroup/dmem: Add queries for protection values

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Callers can use this feedback to be more aggressive in making space for
allocations of a cgroup if they know it is protected.

These are counterparts to memcg's mem_cgroup_below_{min,low}.

Reviewed-by: Maarten Lankhorst <dev@lankhorst.se>
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Signed-off-by: Natalie Vock <natalie.vock@gmx.de>
Link: https://patch.msgid.link/20260804-dmemcg-aggressive-protect-v8-1-07af96681bf8@gmx.de
This commit is contained in:
Natalie Vock 2026-08-04 10:25:16 +02:00 committed by Natalie Vock
parent ae2854a762
commit dd517e49a3
2 changed files with 78 additions and 0 deletions
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16
include/linux/cgroup_dmem.h
View File

@ -24,6 +24,10 @@ void dmem_cgroup_uncharge(struct dmem_cgroup_pool_state *pool, u64 size);
bool dmem_cgroup_state_evict_valuable(struct dmem_cgroup_pool_state *limit_pool,
struct dmem_cgroup_pool_state *test_pool,
bool ignore_low, bool *ret_hit_low);
bool dmem_cgroup_below_min(struct dmem_cgroup_pool_state *root,
struct dmem_cgroup_pool_state *test);
bool dmem_cgroup_below_low(struct dmem_cgroup_pool_state *root,
struct dmem_cgroup_pool_state *test);
void dmem_cgroup_pool_state_put(struct dmem_cgroup_pool_state *pool);
#else
@ -59,6 +63,18 @@ bool dmem_cgroup_state_evict_valuable(struct dmem_cgroup_pool_state *limit_pool,
return true;
}
static inline bool dmem_cgroup_below_min(struct dmem_cgroup_pool_state *root,
struct dmem_cgroup_pool_state *test)
{
return false;
}
static inline bool dmem_cgroup_below_low(struct dmem_cgroup_pool_state *root,
struct dmem_cgroup_pool_state *test)
{
return false;
}
static inline void dmem_cgroup_pool_state_put(struct dmem_cgroup_pool_state *pool)
{ }

62
kernel/cgroup/dmem.c
View File

@ -700,6 +700,68 @@ int dmem_cgroup_try_charge(struct dmem_cgroup_region *region, u64 size,
}
EXPORT_SYMBOL_GPL(dmem_cgroup_try_charge);
/**
* dmem_cgroup_below_min() - Tests whether current usage is within min limit.
*
* @root: Root of the subtree to calculate protection for, or NULL to calculate global protection.
* @test: The pool to test the usage/min limit of.
*
* Return: true if usage is below min and the cgroup is protected, false otherwise.
*/
bool dmem_cgroup_below_min(struct dmem_cgroup_pool_state *root,
struct dmem_cgroup_pool_state *test)
{
if (root == test || !pool_parent(test))
return false;
if (!root) {
for (root = test; pool_parent(root); root = pool_parent(root))
{}
}
/*
* In mem_cgroup_below_min(), the memcg pendant, this call is missing.
* mem_cgroup_below_min() gets called during traversal of the cgroup tree, where
* protection is already calculated as part of the traversal. dmem cgroup eviction
* does not traverse the cgroup tree, so we need to recalculate effective protection
* here.
*/
dmem_cgroup_calculate_protection(root, test);
return page_counter_read(&test->cnt) <= READ_ONCE(test->cnt.emin);
}
EXPORT_SYMBOL_GPL(dmem_cgroup_below_min);
/**
* dmem_cgroup_below_low() - Tests whether current usage is within low limit.
*
* @root: Root of the subtree to calculate protection for, or NULL to calculate global protection.
* @test: The pool to test the usage/low limit of.
*
* Return: true if usage is below low and the cgroup is protected, false otherwise.
*/
bool dmem_cgroup_below_low(struct dmem_cgroup_pool_state *root,
struct dmem_cgroup_pool_state *test)
{
if (root == test || !pool_parent(test))
return false;
if (!root) {
for (root = test; pool_parent(root); root = pool_parent(root))
{}
}
/*
* In mem_cgroup_below_low(), the memcg pendant, this call is missing.
* mem_cgroup_below_low() gets called during traversal of the cgroup tree, where
* protection is already calculated as part of the traversal. dmem cgroup eviction
* does not traverse the cgroup tree, so we need to recalculate effective protection
* here.
*/
dmem_cgroup_calculate_protection(root, test);
return page_counter_read(&test->cnt) <= READ_ONCE(test->cnt.elow);
}
EXPORT_SYMBOL_GPL(dmem_cgroup_below_low);
static int dmem_cgroup_region_capacity_show(struct seq_file *sf, void *v)
{
struct dmem_cgroup_region *region;