From: Hui Zhu <[email protected]> Expose the memory cgroup reclaim interface to BPF programs by adding the bpf_try_to_free_mem_cgroup_pages kfunc. This allows BPF to trigger memory reclamation for a specific cgroup.
The kfunc wraps try_to_free_mem_cgroup_pages and introduces a swappiness parameter with the following semantics: Values in [MIN_SWAPPINESS, SWAPPINESS_ANON_ONLY] are passed through as an explicit swappiness override. Values below MIN_SWAPPINESS indicate the use of the system default (passed as NULL to the core reclaim path). Values above SWAPPINESS_ANON_ONLY are rejected as invalid (-EINVAL). Note that the swappiness override is only respected by the core reclaim path if the MEMCG_RECLAIM_PROACTIVE flag is set in reclaim_options. Swap usage during reclaim is gated on reclaim_options: swap is considered only when MEMCG_RECLAIM_MAY_SWAP is set. Without this flag, reclaim is restricted to file-backed pages regardless of the swappiness value or the cgroup's swappiness setting. Also include <linux/swap.h> for the swappiness macro definitions and register the function with the KF_SLEEPABLE flag. Signed-off-by: Barry Song <[email protected]> Signed-off-by: Geliang Tang <[email protected]> Signed-off-by: Hui Zhu <[email protected]> --- mm/bpf_memcontrol.c | 57 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) diff --git a/mm/bpf_memcontrol.c b/mm/bpf_memcontrol.c index 1f726a7b22e3..0353c8736aa5 100644 --- a/mm/bpf_memcontrol.c +++ b/mm/bpf_memcontrol.c @@ -6,6 +6,7 @@ */ #include <linux/memcontrol.h> +#include <linux/swap.h> #include <linux/bpf.h> /* Protects memcg->bpf_ops pointer for read and write. */ @@ -162,6 +163,60 @@ __bpf_kfunc void bpf_mem_cgroup_flush_stats(struct mem_cgroup *memcg) mem_cgroup_flush_stats(memcg); } +/** + * bpf_try_to_free_mem_cgroup_pages - attempt to reclaim pages from + * a memory cgroup + * @memcg: the target memory cgroup to reclaim from + * @nr_pages: the number of pages to reclaim + * @gfp_mask: GFP flags controlling the reclaim behavior + * @reclaim_options: bitmask of MEMCG_RECLAIM_* flags to tune + * reclaim strategy + * @swappiness: swappiness override value, or a sentinel to use + * the default + * + * BPF-facing wrapper around try_to_free_mem_cgroup_pages() that + * validates and translates the @swappiness argument before + * delegating to the core reclaim path. + * + * The @swappiness parameter follows these semantics: + * - Values in [MIN_SWAPPINESS, SWAPPINESS_ANON_ONLY] are passed + * through as an explicit swappiness override. + * - Values below MIN_SWAPPINESS are treated as "use the system + * default"; the override pointer is set to NULL and the cgroup's + * own swappiness setting takes effect. + * - Values above SWAPPINESS_ANON_ONLY are rejected as invalid. + * - If @reclaim_options does not include MEMCG_RECLAIM_PROACTIVE, + * the @swappiness override is ignored entirely by the core + * reclaim path and the system default is used regardless. + * + * Swap usage during reclaim is gated on @reclaim_options: swap is + * considered only when MEMCG_RECLAIM_MAY_SWAP is set. Without this + * flag, reclaim is restricted to file-backed pages regardless of the + * @swappiness value or the cgroup's swappiness setting. + * + * Return: + * The number of pages actually reclaimed on success, or -%EINVAL + * if @swappiness exceeds SWAPPINESS_ANON_ONLY. + */ +unsigned long bpf_try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, + unsigned long nr_pages, + gfp_t gfp_mask, + unsigned int reclaim_options, + int swappiness) +{ + int *swapiness_ptr; + + if (swappiness > SWAPPINESS_ANON_ONLY) + return -EINVAL; + else if (swappiness < MIN_SWAPPINESS) + swapiness_ptr = NULL; + else + swapiness_ptr = &swappiness; + + return try_to_free_mem_cgroup_pages(memcg, nr_pages, gfp_mask, + reclaim_options, swapiness_ptr); +} + __bpf_kfunc_end_defs(); BTF_KFUNCS_START(bpf_memcontrol_kfuncs) @@ -175,6 +230,8 @@ BTF_ID_FLAGS(func, bpf_mem_cgroup_usage) BTF_ID_FLAGS(func, bpf_mem_cgroup_page_state) BTF_ID_FLAGS(func, bpf_mem_cgroup_flush_stats, KF_SLEEPABLE) +BTF_ID_FLAGS(func, bpf_try_to_free_mem_cgroup_pages, KF_SLEEPABLE) + BTF_KFUNCS_END(bpf_memcontrol_kfuncs) static const struct btf_kfunc_id_set bpf_memcontrol_kfunc_set = { -- 2.43.0
