Daniel Borkmann 4a8f87e60f bpf: Allow for map-in-map with dynamic inner array map entries ... Recent work in f4d0525921 ("bpf: Add map_meta_equal map ops") and 134fede4ee ("bpf: Relax max_entries check for most of the inner map types") added support for dynamic inner max elements for most map-in-map types. Exceptions were maps like array or prog array where the map_gen_lookup() callback uses the maps' max_entries field as a constant when emitting instructions. We recently implemented Maglev consistent hashing into Cilium's load balancer which uses map-in-map with an outer map being hash and inner being array holding the Maglev backend table for each service. This has been designed this way in order to reduce overall memory consumption given the outer hash map allows to avoid preallocating a large, flat memory area for all services. Also, the number of service mappings is not always known a-priori. The use case for dynamic inner array map entries is to further reduce memory overhead, for example, some services might just have a small number of back ends while others could have a large number. Right now the Maglev backend table for small and large number of backends would need to have the same inner array map entries which adds a lot of unneeded overhead. Dynamic inner array map entries can be realized by avoiding the inlined code generation for their lookup. The lookup will still be efficient since it will be calling into array_map_lookup_elem() directly and thus avoiding retpoline. The patch adds a BPF_F_INNER_MAP flag to map creation which therefore skips inline code generation and relaxes array_map_meta_equal() check to ignore both maps' max_entries. This also still allows to have faster lookups for map-in-map when BPF_F_INNER_MAP is not specified and hence dynamic max_entries not needed. Example code generation where inner map is dynamic sized array: # bpftool p d x i 125 int handle__sys_enter(void * ctx): ; int handle__sys_enter(void *ctx) 0: (b4) w1 = 0 ; int key = 0; 1: (63) *(u32 *)(r10 -4) = r1 2: (bf) r2 = r10 ; 3: (07) r2 += -4 ; inner_map = bpf_map_lookup_elem(&outer_arr_dyn, &key); 4: (18) r1 = map[id:468] 6: (07) r1 += 272 7: (61) r0 = *(u32 *)(r2 +0) 8: (35) if r0 >= 0x3 goto pc+5 9: (67) r0 <<= 3 10: (0f) r0 += r1 11: (79) r0 = *(u64 *)(r0 +0) 12: (15) if r0 == 0x0 goto pc+1 13: (05) goto pc+1 14: (b7) r0 = 0 15: (b4) w6 = -1 ; if (!inner_map) 16: (15) if r0 == 0x0 goto pc+6 17: (bf) r2 = r10 ; 18: (07) r2 += -4 ; val = bpf_map_lookup_elem(inner_map, &key); 19: (bf) r1 = r0 | No inlining but instead 20: (85) call array_map_lookup_elem#149280 | call to array_map_lookup_elem() ; return val ? *val : -1; | for inner array lookup. 21: (15) if r0 == 0x0 goto pc+1 ; return val ? *val : -1; 22: (61) r6 = *(u32 *)(r0 +0) ; } 23: (bc) w0 = w6 24: (95) exit Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20201010234006.7075-4-daniel@iogearbox.net		2020-10-11 10:21:04 -07:00
..
accounting
arch	tools headers kvm s390: Sync headers with the kernel sources	2020-08-12 08:52:32 -03:00
bootconfig	tools/bootconfig: Add testcases for value override operator	2020-08-03 16:22:29 -04:00
bpf	Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next	2020-09-23 13:11:11 -07:00
build	tools, bpf/build: Cleanup feature files on make clean	2020-08-28 14:04:27 +02:00
cgroup	tools/cgroup: add memcg_slabinfo.py tool	2020-08-07 11:33:25 -07:00
debugging
edid
firewire
firmware
gpio	tools: gpio: fix spurious close warning in gpio-event-mon	2020-07-12 10:22:01 +02:00
hv	tools: hv: change http to https in hv_kvp_daemon.c	2020-07-06 10:46:23 +00:00
iio
include	bpf: Allow for map-in-map with dynamic inner array map entries	2020-10-11 10:21:04 -07:00
io_uring	tools/io_uring: fix compile breakage	2020-09-21 07:50:58 -06:00
kvm/kvm_stat
laptop
leds
lib	libbpf: Allow specifying both ELF and raw BTF for CO-RE BTF override	2020-10-07 18:50:27 -07:00
memory-model	These were the main changes in this cycle:	2020-08-03 14:39:35 -07:00
nfsd
objtool	objtool: Fix noreturn detection for ignored functions	2020-09-18 19:37:51 +02:00
pci
pcmcia
perf	Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next	2020-09-23 13:11:11 -07:00
power	ACPI updates for 5.9-rc1	2020-08-03 20:37:22 -07:00
scripts
spi
testing	selftests/bpf: Asm tests for the verifier regalloc tracking.	2020-10-09 22:03:06 +02:00
thermal/tmon
time
usb	tools: usb: move to tools buildsystem	2020-08-19 14:11:44 +02:00
virtio	virtio: fixes, features	2020-08-11 14:34:17 -07:00
vm
wmi
Makefile	bpf: Compile resolve_btfids tool at kernel compilation start	2020-07-13 10:42:02 -07:00