Commit 5b95e638 authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov
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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: default avatarHou Tao <houtao1@huawei.com>
Signed-off-by: default avatarYonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20231222031750.1289290-1-yonghong.song@linux.dev


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent c39aa3b2

kernel/bpf/memalloc.c

+9 −4
Original line number Diff line number Diff line
@@ -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.