From: Yonghong Song Date: Fri, 22 Dec 2023 03:17:50 +0000 (-0800) Subject: bpf: Refill only one percpu element in memalloc X-Git-Tag: v6.8-rc1~131^2~17^2~6^2~4 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5b95e638f134e552b5ba2976326c02babe248615;p=thirdparty%2Fkernel%2Flinux.git bpf: Refill only one percpu element in memalloc Typically for percpu map element or data structure, once allocated, most operations are lookup or in-place update. Deletion are really rare. Currently, for percpu data strcture, 4 elements will be refilled if the size is <= 256. Let us just do with one element for percpu data. For example, for size 256 and 128 cpus, the potential saving will be 3 * 256 * 128 * 128 = 12MB. Acked-by: Hou Tao Signed-off-by: Yonghong Song Link: https://lore.kernel.org/r/20231222031750.1289290-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov --- diff --git a/kernel/bpf/memalloc.c b/kernel/bpf/memalloc.c index f71da07eb8a01..a8ee6fb8401c9 100644 --- a/kernel/bpf/memalloc.c +++ b/kernel/bpf/memalloc.c @@ -485,11 +485,16 @@ static void init_refill_work(struct bpf_mem_cache *c) static void prefill_mem_cache(struct bpf_mem_cache *c, int cpu) { - /* To avoid consuming memory assume that 1st run of bpf - * prog won't be doing more than 4 map_update_elem from - * irq disabled region + int cnt = 1; + + /* To avoid consuming memory, for non-percpu allocation, assume that + * 1st run of bpf prog won't be doing more than 4 map_update_elem from + * irq disabled region if unit size is less than or equal to 256. + * For all other cases, let us just do one allocation. */ - alloc_bulk(c, c->unit_size <= 256 ? 4 : 1, cpu_to_node(cpu), false); + if (!c->percpu_size && c->unit_size <= 256) + cnt = 4; + alloc_bulk(c, cnt, cpu_to_node(cpu), false); } /* When size != 0 bpf_mem_cache for each cpu.