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  1. 29 Jun, 2022 5 commits
    • Stanislav Fomichev's avatar
      bpf: implement BPF_PROG_QUERY for BPF_LSM_CGROUP · b79c9fc9
      Stanislav Fomichev authored 
      We have two options:
1. Treat all BPF_LSM_CGROUP the same, regardless of attach_btf_id
2. Treat BPF_LSM_CGROUP+attach_btf_id as a separate hook point

I was doing (2) in the original patch, but switching to (1) here:

* bpf_prog_query returns all attached BPF_LSM_CGROUP programs
regardless of attach_btf_id
* attach_btf_id is exported via bpf_prog_info
Reviewed-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarStanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20220628174314.1216643-6-sdf@google.comSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      b79c9fc9
    • Stanislav Fomichev's avatar
      bpf: minimize number of allocated lsm slots per program · c0e19f2c
      Stanislav Fomichev authored 
      Previous patch adds 1:1 mapping between all 211 LSM hooks
and bpf_cgroup program array. Instead of reserving a slot per
possible hook, reserve 10 slots per cgroup for lsm programs.
Those slots are dynamically allocated on demand and reclaimed.

struct cgroup_bpf {
	struct bpf_prog_array *    effective[33];        /*     0   264 */
	/* --- cacheline 4 boundary (256 bytes) was 8 bytes ago --- */
	struct hlist_head          progs[33];            /*   264   264 */
	/* --- cacheline 8 boundary (512 bytes) was 16 bytes ago --- */
	u8                         flags[33];            /*   528    33 */

	/* XXX 7 bytes hole, try to pack */

	struct list_head           storages;             /*   568    16 */
	/* --- cacheline 9 boundary (576 bytes) was 8 bytes ago --- */
	struct bpf_prog_array *    inactive;             /*   584     8 */
	struct percpu_ref          refcnt;               /*   592    16 */
	struct work_struct         release_work;         /*   608    72 */

	/* size: 680, cachelines: 11, members: 7 */
	/* sum members: 673, holes: 1, sum holes: 7 */
	/* last cacheline: 40 bytes */
};
Reviewed-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarStanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20220628174314.1216643-5-sdf@google.comSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      c0e19f2c
    • Stanislav Fomichev's avatar
      bpf: per-cgroup lsm flavor · 69fd337a
      Stanislav Fomichev authored 
      Allow attaching to lsm hooks in the cgroup context.

Attaching to per-cgroup LSM works exactly like attaching
to other per-cgroup hooks. New BPF_LSM_CGROUP is added
to trigger new mode; the actual lsm hook we attach to is
signaled via existing attach_btf_id.

For the hooks that have 'struct socket' or 'struct sock' as its first
argument, we use the cgroup associated with that socket. For the rest,
we use 'current' cgroup (this is all on default hierarchy == v2 only).
Note that for some hooks that work on 'struct sock' we still
take the cgroup from 'current' because some of them work on the socket
that hasn't been properly initialized yet.

Behind the scenes, we allocate a shim program that is attached
to the trampoline and runs cgroup effective BPF programs array.
This shim has some rudimentary ref counting and can be shared
between several programs attaching to the same lsm hook from
different cgroups.

Note that this patch bloats cgroup size because we add 211
cgroup_bpf_attach_type(s) for simplicity sake. This will be
addressed in the subsequent patch.

Also note that we only add non-sleepable flavor for now. To enable
sleepable use-cases, bpf_prog_run_array_cg has to grab trace rcu,
shim programs have to be freed via trace rcu, cgroup_bpf.effective
should be also trace-rcu-managed + maybe some other changes that
I'm not aware of.
Reviewed-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarStanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20220628174314.1216643-4-sdf@google.comSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      69fd337a
    • Stanislav Fomichev's avatar
      bpf: convert cgroup_bpf.progs to hlist · 00442143
      Stanislav Fomichev authored 
      This lets us reclaim some space to be used by new cgroup lsm slots.

Before:
struct cgroup_bpf {
	struct bpf_prog_array *    effective[23];        /*     0   184 */
	/* --- cacheline 2 boundary (128 bytes) was 56 bytes ago --- */
	struct list_head           progs[23];            /*   184   368 */
	/* --- cacheline 8 boundary (512 bytes) was 40 bytes ago --- */
	u32                        flags[23];            /*   552    92 */

	/* XXX 4 bytes hole, try to pack */

	/* --- cacheline 10 boundary (640 bytes) was 8 bytes ago --- */
	struct list_head           storages;             /*   648    16 */
	struct bpf_prog_array *    inactive;             /*   664     8 */
	struct percpu_ref          refcnt;               /*   672    16 */
	struct work_struct         release_work;         /*   688    32 */

	/* size: 720, cachelines: 12, members: 7 */
	/* sum members: 716, holes: 1, sum holes: 4 */
	/* last cacheline: 16 bytes */
};

After:
struct cgroup_bpf {
	struct bpf_prog_array *    effective[23];        /*     0   184 */
	/* --- cacheline 2 boundary (128 bytes) was 56 bytes ago --- */
	struct hlist_head          progs[23];            /*   184   184 */
	/* --- cacheline 5 boundary (320 bytes) was 48 bytes ago --- */
	u8                         flags[23];            /*   368    23 */

	/* XXX 1 byte hole, try to pack */

	/* --- cacheline 6 boundary (384 bytes) was 8 bytes ago --- */
	struct list_head           storages;             /*   392    16 */
	struct bpf_prog_array *    inactive;             /*   408     8 */
	struct percpu_ref          refcnt;               /*   416    16 */
	struct work_struct         release_work;         /*   432    72 */

	/* size: 504, cachelines: 8, members: 7 */
	/* sum members: 503, holes: 1, sum holes: 1 */
	/* last cacheline: 56 bytes */
};
Suggested-by: default avatarJakub Sitnicki <jakub@cloudflare.com>
Reviewed-by: default avatarJakub Sitnicki <jakub@cloudflare.com>
Reviewed-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarStanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20220628174314.1216643-3-sdf@google.comSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      00442143
    • Stanislav Fomichev's avatar
      bpf: add bpf_func_t and trampoline helpers · af3f4134
      Stanislav Fomichev authored 
      I'll be adding lsm cgroup specific helpers that grab
trampoline mutex.

No functional changes.
Reviewed-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarStanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20220628174314.1216643-2-sdf@google.comSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      af3f4134
  3. 28 Jun, 2022 17 commits
  5. 24 Jun, 2022 7 commits
  7. 23 Jun, 2022 9 commits
    • Jörn-Thorben Hinz's avatar
      selftests/bpf: Fix rare segfault in sock_fields prog test · 6dc7a0ba
      Jörn-Thorben Hinz authored 
      test_sock_fields__detach() got called with a null pointer here when one
of the CHECKs or ASSERTs up to the test_sock_fields__open_and_load()
call resulted in a jump to the "done" label.

A skeletons *__detach() is not safe to call with a null pointer, though.
This led to a segfault.

Go the easy route and only call test_sock_fields__destroy() which is
null-pointer safe and includes detaching.

Came across this while looking[1] to introduce the usage of
bpf_tcp_helpers.h (included in progs/test_sock_fields.c) together with
vmlinux.h.

[1] https://lore.kernel.org/bpf/629bc069dd807d7ac646f836e9dca28bbc1108e2.camel@mailbox.tu-berlin.de/

Fixes: 8f50f16f ("selftests/bpf: Extend verifier and bpf_sock tests for dst_port loads")
Signed-off-by: default avatarJörn-Thorben Hinz <jthinz@mailbox.tu-berlin.de>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Reviewed-by: default avatarJakub Sitnicki <jakub@cloudflare.com>
Reviewed-by: default avatarMartin KaFai Lau <kafai@fb.com>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20220621070116.307221-1-jthinz@mailbox.tu-berlin.de
      6dc7a0ba
    • Alexei Starovoitov's avatar
      Merge branch 'Align BPF TCP CCs implementing cong_control() with non-BPF CCs' · bb7a4257
      Alexei Starovoitov authored 
      Jörn-Thorben Hinz says:

====================

This series corrects some inconveniences for a BPF TCP CC that
implements and uses tcp_congestion_ops.cong_control(). Until now, such a
CC did not have all necessary write access to struct sock and
unnecessarily needed to implement cong_avoid().

v4:
 - Remove braces around single statements after if
 - Don’t check pointer passed to bpf_link__destroy()
v3:
 - Add a selftest writing sk_pacing_*
 - Add a selftest with incomplete tcp_congestion_ops
 - Add a selftest with unsupported get_info()
 - Remove an unused variable
 - Reword a comment about reg() in bpf_struct_ops_map_update_elem()
v2:
 - Drop redundant check for required functions and just rely on
   tcp_register_congestion_control() (Martin KaFai Lau)
====================
Reviewed-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      bb7a4257
    • Jörn-Thorben Hinz's avatar
      selftests/bpf: Test a BPF CC implementing the unsupported get_info() · f14a3f64
      Jörn-Thorben Hinz authored 
      Test whether a TCP CC implemented in BPF providing get_info() is
rejected correctly. get_info() is unsupported in a BPF CC. The check for
required functions in a BPF CC has moved, this test ensures unsupported
functions are still rejected correctly.
Signed-off-by: default avatarJörn-Thorben Hinz <jthinz@mailbox.tu-berlin.de>
Reviewed-by: default avatarMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/r/20220622191227.898118-6-jthinz@mailbox.tu-berlin.deSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      f14a3f64
    • Jörn-Thorben Hinz's avatar
      selftests/bpf: Test an incomplete BPF CC · 0735627d
      Jörn-Thorben Hinz authored 
      Test whether a TCP CC implemented in BPF providing neither cong_avoid()
nor cong_control() is correctly rejected. This check solely depends on
tcp_register_congestion_control() now, which is invoked during
bpf_map__attach_struct_ops().
Signed-off-by: default avatarJörn-Thorben Hinz <jthinz@mailbox.tu-berlin.de>
Link: https://lore.kernel.org/r/20220622191227.898118-5-jthinz@mailbox.tu-berlin.deSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      0735627d
    • Jörn-Thorben Hinz's avatar
      selftests/bpf: Test a BPF CC writing sk_pacing_* · 6e945d57
      Jörn-Thorben Hinz authored 
      Test whether a TCP CC implemented in BPF is allowed to write
sk_pacing_rate and sk_pacing_status in struct sock. This is needed when
cong_control() is implemented and used.
Signed-off-by: default avatarJörn-Thorben Hinz <jthinz@mailbox.tu-berlin.de>
Link: https://lore.kernel.org/r/20220622191227.898118-4-jthinz@mailbox.tu-berlin.deSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      6e945d57
    • Jörn-Thorben Hinz's avatar
      bpf: Require only one of cong_avoid() and cong_control() from a TCP CC · 9f0265e9
      Jörn-Thorben Hinz authored 
      Remove the check for required and optional functions in a struct
tcp_congestion_ops from bpf_tcp_ca.c. Rely on
tcp_register_congestion_control() to reject a BPF CC that does not
implement all required functions, as it will do for a non-BPF CC.

When a CC implements tcp_congestion_ops.cong_control(), the alternate
cong_avoid() is not in use in the TCP stack. Previously, a BPF CC was
still forced to implement cong_avoid() as a no-op since it was
non-optional in bpf_tcp_ca.c.
Signed-off-by: default avatarJörn-Thorben Hinz <jthinz@mailbox.tu-berlin.de>
Reviewed-by: default avatarMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/r/20220622191227.898118-3-jthinz@mailbox.tu-berlin.deSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      9f0265e9
    • Jörn-Thorben Hinz's avatar
      bpf: Allow a TCP CC to write sk_pacing_rate and sk_pacing_status · 41c95dd6
      Jörn-Thorben Hinz authored 
      A CC that implements tcp_congestion_ops.cong_control() should be able to
control sk_pacing_rate and set sk_pacing_status, since
tcp_update_pacing_rate() is never called in this case. A built-in CC or
one from a kernel module is already able to write to both struct sock
members. For a BPF program, write access has not been allowed, yet.
Signed-off-by: default avatarJörn-Thorben Hinz <jthinz@mailbox.tu-berlin.de>
Reviewed-by: default avatarMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/r/20220622191227.898118-2-jthinz@mailbox.tu-berlin.deSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      41c95dd6
    • Jian Shen's avatar
      test_bpf: fix incorrect netdev features · 9676fecc
      Jian Shen authored 
      The prototype of .features is netdev_features_t, it should use
NETIF_F_LLTX and NETIF_F_HW_VLAN_STAG_TX, not NETIF_F_LLTX_BIT
and NETIF_F_HW_VLAN_STAG_TX_BIT.

Fixes: cf204a71 ("bpf, testing: Introduce 'gso_linear_no_head_frag' skb_segment test")
Signed-off-by: default avatarJian Shen <shenjian15@huawei.com>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/r/20220622135002.8263-1-shenjian15@huawei.comSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      9676fecc
    • Dave Marchevsky's avatar
      selftests/bpf: Add benchmark for local_storage get · 73087489
      Dave Marchevsky authored 
      Add a benchmarks to demonstrate the performance cliff for local_storage
get as the number of local_storage maps increases beyond current
local_storage implementation's cache size.

"sequential get" and "interleaved get" benchmarks are added, both of
which do many bpf_task_storage_get calls on sets of task local_storage
maps of various counts, while considering a single specific map to be
'important' and counting task_storage_gets to the important map
separately in addition to normal 'hits' count of all gets. Goal here is
to mimic scenario where a particular program using one map - the
important one - is running on a system where many other local_storage
maps exist and are accessed often.

While "sequential get" benchmark does bpf_task_storage_get for map 0, 1,
..., {9, 99, 999} in order, "interleaved" benchmark interleaves 4
bpf_task_storage_gets for the important map for every 10 map gets. This
is meant to highlight performance differences when important map is
accessed far more frequently than non-important maps.

A "hashmap control" benchmark is also included for easy comparison of
standard bpf hashmap lookup vs local_storage get. The benchmark is
similar to "sequential get", but creates and uses BPF_MAP_TYPE_HASH
instead of local storage. Only one inner map is created - a hashmap
meant to hold tid -> data mapping for all tasks. Size of the hashmap is
hardcoded to my system's PID_MAX_LIMIT (4,194,304). The number of these
keys which are actually fetched as part of the benchmark is
configurable.

Addition of this benchmark is inspired by conversation with Alexei in a
previous patchset's thread [0], which highlighted the need for such a
benchmark to motivate and validate improvements to local_storage
implementation. My approach in that series focused on improving
performance for explicitly-marked 'important' maps and was rejected
with feedback to make more generally-applicable improvements while
avoiding explicitly marking maps as important. Thus the benchmark
reports both general and important-map-focused metrics, so effect of
future work on both is clear.

Regarding the benchmark results. On a powerful system (Skylake, 20
cores, 256gb ram):

Hashmap Control
===============
        num keys: 10
hashmap (control) sequential    get:  hits throughput: 20.900 ± 0.334 M ops/s, hits latency: 47.847 ns/op, important_hits throughput: 20.900 ± 0.334 M ops/s

        num keys: 1000
hashmap (control) sequential    get:  hits throughput: 13.758 ± 0.219 M ops/s, hits latency: 72.683 ns/op, important_hits throughput: 13.758 ± 0.219 M ops/s

        num keys: 10000
hashmap (control) sequential    get:  hits throughput: 6.995 ± 0.034 M ops/s, hits latency: 142.959 ns/op, important_hits throughput: 6.995 ± 0.034 M ops/s

        num keys: 100000
hashmap (control) sequential    get:  hits throughput: 4.452 ± 0.371 M ops/s, hits latency: 224.635 ns/op, important_hits throughput: 4.452 ± 0.371 M ops/s

        num keys: 4194304
hashmap (control) sequential    get:  hits throughput: 3.043 ± 0.033 M ops/s, hits latency: 328.587 ns/op, important_hits throughput: 3.043 ± 0.033 M ops/s

Local Storage
=============
        num_maps: 1
local_storage cache sequential  get:  hits throughput: 47.298 ± 0.180 M ops/s, hits latency: 21.142 ns/op, important_hits throughput: 47.298 ± 0.180 M ops/s
local_storage cache interleaved get:  hits throughput: 55.277 ± 0.888 M ops/s, hits latency: 18.091 ns/op, important_hits throughput: 55.277 ± 0.888 M ops/s

        num_maps: 10
local_storage cache sequential  get:  hits throughput: 40.240 ± 0.802 M ops/s, hits latency: 24.851 ns/op, important_hits throughput: 4.024 ± 0.080 M ops/s
local_storage cache interleaved get:  hits throughput: 48.701 ± 0.722 M ops/s, hits latency: 20.533 ns/op, important_hits throughput: 17.393 ± 0.258 M ops/s

        num_maps: 16
local_storage cache sequential  get:  hits throughput: 44.515 ± 0.708 M ops/s, hits latency: 22.464 ns/op, important_hits throughput: 2.782 ± 0.044 M ops/s
local_storage cache interleaved get:  hits throughput: 49.553 ± 2.260 M ops/s, hits latency: 20.181 ns/op, important_hits throughput: 15.767 ± 0.719 M ops/s

        num_maps: 17
local_storage cache sequential  get:  hits throughput: 38.778 ± 0.302 M ops/s, hits latency: 25.788 ns/op, important_hits throughput: 2.284 ± 0.018 M ops/s
local_storage cache interleaved get:  hits throughput: 43.848 ± 1.023 M ops/s, hits latency: 22.806 ns/op, important_hits throughput: 13.349 ± 0.311 M ops/s

        num_maps: 24
local_storage cache sequential  get:  hits throughput: 19.317 ± 0.568 M ops/s, hits latency: 51.769 ns/op, important_hits throughput: 0.806 ± 0.024 M ops/s
local_storage cache interleaved get:  hits throughput: 24.397 ± 0.272 M ops/s, hits latency: 40.989 ns/op, important_hits throughput: 6.863 ± 0.077 M ops/s

        num_maps: 32
local_storage cache sequential  get:  hits throughput: 13.333 ± 0.135 M ops/s, hits latency: 75.000 ns/op, important_hits throughput: 0.417 ± 0.004 M ops/s
local_storage cache interleaved get:  hits throughput: 16.898 ± 0.383 M ops/s, hits latency: 59.178 ns/op, important_hits throughput: 4.717 ± 0.107 M ops/s

        num_maps: 100
local_storage cache sequential  get:  hits throughput: 6.360 ± 0.107 M ops/s, hits latency: 157.233 ns/op, important_hits throughput: 0.064 ± 0.001 M ops/s
local_storage cache interleaved get:  hits throughput: 7.303 ± 0.362 M ops/s, hits latency: 136.930 ns/op, important_hits throughput: 1.907 ± 0.094 M ops/s

        num_maps: 1000
local_storage cache sequential  get:  hits throughput: 0.452 ± 0.010 M ops/s, hits latency: 2214.022 ns/op, important_hits throughput: 0.000 ± 0.000 M ops/s
local_storage cache interleaved get:  hits throughput: 0.542 ± 0.007 M ops/s, hits latency: 1843.341 ns/op, important_hits throughput: 0.136 ± 0.002 M ops/s

Looking at the "sequential get" results, it's clear that as the
number of task local_storage maps grows beyond the current cache size
(16), there's a significant reduction in hits throughput. Note that
current local_storage implementation assigns a cache_idx to maps as they
are created. Since "sequential get" is creating maps 0..n in order and
then doing bpf_task_storage_get calls in the same order, the benchmark
is effectively ensuring that a map will not be in cache when the program
tries to access it.

For "interleaved get" results, important-map hits throughput is greatly
increased as the important map is more likely to be in cache by virtue
of being accessed far more frequently. Throughput still reduces as #
maps increases, though.

To get a sense of the overhead of the benchmark program, I
commented out bpf_task_storage_get/bpf_map_lookup_elem in
local_storage_bench.c and ran the benchmark on the same host as the
'real' run. Results:

Hashmap Control
===============
        num keys: 10
hashmap (control) sequential    get:  hits throughput: 54.288 ± 0.655 M ops/s, hits latency: 18.420 ns/op, important_hits throughput: 54.288 ± 0.655 M ops/s

        num keys: 1000
hashmap (control) sequential    get:  hits throughput: 52.913 ± 0.519 M ops/s, hits latency: 18.899 ns/op, important_hits throughput: 52.913 ± 0.519 M ops/s

        num keys: 10000
hashmap (control) sequential    get:  hits throughput: 53.480 ± 1.235 M ops/s, hits latency: 18.699 ns/op, important_hits throughput: 53.480 ± 1.235 M ops/s

        num keys: 100000
hashmap (control) sequential    get:  hits throughput: 54.982 ± 1.902 M ops/s, hits latency: 18.188 ns/op, important_hits throughput: 54.982 ± 1.902 M ops/s

        num keys: 4194304
hashmap (control) sequential    get:  hits throughput: 50.858 ± 0.707 M ops/s, hits latency: 19.662 ns/op, important_hits throughput: 50.858 ± 0.707 M ops/s

Local Storage
=============
        num_maps: 1
local_storage cache sequential  get:  hits throughput: 110.990 ± 4.828 M ops/s, hits latency: 9.010 ns/op, important_hits throughput: 110.990 ± 4.828 M ops/s
local_storage cache interleaved get:  hits throughput: 161.057 ± 4.090 M ops/s, hits latency: 6.209 ns/op, important_hits throughput: 161.057 ± 4.090 M ops/s

        num_maps: 10
local_storage cache sequential  get:  hits throughput: 112.930 ± 1.079 M ops/s, hits latency: 8.855 ns/op, important_hits throughput: 11.293 ± 0.108 M ops/s
local_storage cache interleaved get:  hits throughput: 115.841 ± 2.088 M ops/s, hits latency: 8.633 ns/op, important_hits throughput: 41.372 ± 0.746 M ops/s

        num_maps: 16
local_storage cache sequential  get:  hits throughput: 115.653 ± 0.416 M ops/s, hits latency: 8.647 ns/op, important_hits throughput: 7.228 ± 0.026 M ops/s
local_storage cache interleaved get:  hits throughput: 138.717 ± 1.649 M ops/s, hits latency: 7.209 ns/op, important_hits throughput: 44.137 ± 0.525 M ops/s

        num_maps: 17
local_storage cache sequential  get:  hits throughput: 112.020 ± 1.649 M ops/s, hits latency: 8.927 ns/op, important_hits throughput: 6.598 ± 0.097 M ops/s
local_storage cache interleaved get:  hits throughput: 128.089 ± 1.960 M ops/s, hits latency: 7.807 ns/op, important_hits throughput: 38.995 ± 0.597 M ops/s

        num_maps: 24
local_storage cache sequential  get:  hits throughput: 92.447 ± 5.170 M ops/s, hits latency: 10.817 ns/op, important_hits throughput: 3.855 ± 0.216 M ops/s
local_storage cache interleaved get:  hits throughput: 128.844 ± 2.808 M ops/s, hits latency: 7.761 ns/op, important_hits throughput: 36.245 ± 0.790 M ops/s

        num_maps: 32
local_storage cache sequential  get:  hits throughput: 102.042 ± 1.462 M ops/s, hits latency: 9.800 ns/op, important_hits throughput: 3.194 ± 0.046 M ops/s
local_storage cache interleaved get:  hits throughput: 126.577 ± 1.818 M ops/s, hits latency: 7.900 ns/op, important_hits throughput: 35.332 ± 0.507 M ops/s

        num_maps: 100
local_storage cache sequential  get:  hits throughput: 111.327 ± 1.401 M ops/s, hits latency: 8.983 ns/op, important_hits throughput: 1.113 ± 0.014 M ops/s
local_storage cache interleaved get:  hits throughput: 131.327 ± 1.339 M ops/s, hits latency: 7.615 ns/op, important_hits throughput: 34.302 ± 0.350 M ops/s

        num_maps: 1000
local_storage cache sequential  get:  hits throughput: 101.978 ± 0.563 M ops/s, hits latency: 9.806 ns/op, important_hits throughput: 0.102 ± 0.001 M ops/s
local_storage cache interleaved get:  hits throughput: 141.084 ± 1.098 M ops/s, hits latency: 7.088 ns/op, important_hits throughput: 35.430 ± 0.276 M ops/s

Adjusting for overhead, latency numbers for "hashmap control" and
"sequential get" are:

hashmap_control_1k:   ~53.8ns
hashmap_control_10k:  ~124.2ns
hashmap_control_100k: ~206.5ns
sequential_get_1:     ~12.1ns
sequential_get_10:    ~16.0ns
sequential_get_16:    ~13.8ns
sequential_get_17:    ~16.8ns
sequential_get_24:    ~40.9ns
sequential_get_32:    ~65.2ns
sequential_get_100:   ~148.2ns
sequential_get_1000:  ~2204ns

Clearly demonstrating a cliff.

In the discussion for v1 of this patch, Alexei noted that local_storage
was 2.5x faster than a large hashmap when initially implemented [1]. The
benchmark results show that local_storage is 5-10x faster: a
long-running BPF application putting some pid-specific info into a
hashmap for each pid it sees will probably see on the order of 10-100k
pids. Bench numbers for hashmaps of this size are ~10x slower than
sequential_get_16, but as the number of local_storage maps grows far
past local_storage cache size the performance advantage shrinks and
eventually reverses.

When running the benchmarks it may be necessary to bump 'open files'
ulimit for a successful run.

  [0]: https://lore.kernel.org/all/20220420002143.1096548-1-davemarchevsky@fb.com
  [1]: https://lore.kernel.org/bpf/20220511173305.ftldpn23m4ski3d3@MBP-98dd607d3435.dhcp.thefacebook.com/Signed-off-by: default avatarDave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/r/20220620222554.270578-1-davemarchevsky@fb.comSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      73087489
  9. 22 Jun, 2022 1 commit
  11. 21 Jun, 2022 1 commit
    • Jakub Sitnicki's avatar
      bpf, arm64: Keep tail call count across bpf2bpf calls · d4609a5d
      Jakub Sitnicki authored 
      Today doing a BPF tail call after a BPF to BPF call, that is from a
subprogram, is allowed only by the x86-64 BPF JIT. Mixing these features
requires support from JIT. Tail call count has to be tracked through BPF to
BPF calls, as well as through BPF tail calls to prevent unbounded chains of
tail calls.

arm64 BPF JIT stores the tail call count (TCC) in a dedicated
register (X26). This makes it easier to support bpf2bpf calls mixed with
tail calls than on x86 platform.

In order to keep the tail call count in tact throughout bpf2bpf calls, all
we need to do is tweak the program prologue generator. When emitting
prologue for a subprogram, we skip the block that initializes the tail call
count and emits a jump pad for the tail call.

With this change, a sample execution flow where a bpf2bpf call is followed
by a tail call would look like so:

int entry(struct __sk_buff *skb):
   0xffffffc0090151d4:  paciasp
   0xffffffc0090151d8:  stp     x29, x30, [sp, #-16]!
   0xffffffc0090151dc:  mov     x29, sp
   0xffffffc0090151e0:  stp     x19, x20, [sp, #-16]!
   0xffffffc0090151e4:  stp     x21, x22, [sp, #-16]!
   0xffffffc0090151e8:  stp     x25, x26, [sp, #-16]!
   0xffffffc0090151ec:  stp     x27, x28, [sp, #-16]!
   0xffffffc0090151f0:  mov     x25, sp
   0xffffffc0090151f4:  mov     x26, #0x0                       // <- init TCC only
   0xffffffc0090151f8:  bti     j                               //    in main prog
   0xffffffc0090151fc:  sub     x27, x25, #0x0
   0xffffffc009015200:  sub     sp, sp, #0x10
   0xffffffc009015204:  mov     w1, #0x0
   0xffffffc009015208:  mov     x10, #0xffffffffffffffff
   0xffffffc00901520c:  strb    w1, [x25, x10]
   0xffffffc009015210:  mov     x10, #0xffffffffffffd25c
   0xffffffc009015214:  movk    x10, #0x902, lsl #16
   0xffffffc009015218:  movk    x10, #0xffc0, lsl #32
   0xffffffc00901521c:  blr     x10 -------------------.        // bpf2bpf call
   0xffffffc009015220:  add     x7, x0, #0x0 <-------------.
   0xffffffc009015224:  add     sp, sp, #0x10          |   |
   0xffffffc009015228:  ldp     x27, x28, [sp], #16    |   |
   0xffffffc00901522c:  ldp     x25, x26, [sp], #16    |   |
   0xffffffc009015230:  ldp     x21, x22, [sp], #16    |   |
   0xffffffc009015234:  ldp     x19, x20, [sp], #16    |   |
   0xffffffc009015238:  ldp     x29, x30, [sp], #16    |   |
   0xffffffc00901523c:  add     x0, x7, #0x0           |   |
   0xffffffc009015240:  autiasp                        |   |
   0xffffffc009015244:  ret                            |   |
                                                       |   |
int subprog_tail(struct __sk_buff *skb):               |   |
   0xffffffc00902d25c:  paciasp <----------------------'   |
   0xffffffc00902d260:  stp     x29, x30, [sp, #-16]!      |
   0xffffffc00902d264:  mov     x29, sp                    |
   0xffffffc00902d268:  stp     x19, x20, [sp, #-16]!      |
   0xffffffc00902d26c:  stp     x21, x22, [sp, #-16]!      |
   0xffffffc00902d270:  stp     x25, x26, [sp, #-16]!      |
   0xffffffc00902d274:  stp     x27, x28, [sp, #-16]!      |
   0xffffffc00902d278:  mov     x25, sp                    |
   0xffffffc00902d27c:  sub     x27, x25, #0x0             |
   0xffffffc00902d280:  sub     sp, sp, #0x10              |    // <- end of prologue, notice:
   0xffffffc00902d284:  add     x19, x0, #0x0              |    //    1) TCC not touched, and
   0xffffffc00902d288:  mov     w0, #0x1                   |    //    2) no tail call jump pad
   0xffffffc00902d28c:  mov     x10, #0xfffffffffffffffc   |
   0xffffffc00902d290:  str     w0, [x25, x10]             |
   0xffffffc00902d294:  mov     x20, #0xffffff80ffffffff   |
   0xffffffc00902d298:  movk    x20, #0xc033, lsl #16      |
   0xffffffc00902d29c:  movk    x20, #0x4e00               |
   0xffffffc00902d2a0:  add     x0, x19, #0x0              |
   0xffffffc00902d2a4:  add     x1, x20, #0x0              |
   0xffffffc00902d2a8:  mov     x2, #0x0                   |
   0xffffffc00902d2ac:  mov     w10, #0x24                 |
   0xffffffc00902d2b0:  ldr     w10, [x1, x10]             |
   0xffffffc00902d2b4:  add     w2, w2, #0x0               |
   0xffffffc00902d2b8:  cmp     w2, w10                    |
   0xffffffc00902d2bc:  b.cs    0xffffffc00902d2f8         |
   0xffffffc00902d2c0:  mov     w10, #0x21                 |
   0xffffffc00902d2c4:  cmp     x26, x10                   |    // TCC >= MAX_TAIL_CALL_CNT?
   0xffffffc00902d2c8:  b.cs    0xffffffc00902d2f8         |
   0xffffffc00902d2cc:  add     x26, x26, #0x1             |    // TCC++
   0xffffffc00902d2d0:  mov     w10, #0x110                |
   0xffffffc00902d2d4:  add     x10, x1, x10               |
   0xffffffc00902d2d8:  lsl     x11, x2, #3                |
   0xffffffc00902d2dc:  ldr     x11, [x10, x11]            |
   0xffffffc00902d2e0:  cbz     x11, 0xffffffc00902d2f8    |
   0xffffffc00902d2e4:  mov     w10, #0x30                 |
   0xffffffc00902d2e8:  ldr     x10, [x11, x10]            |
   0xffffffc00902d2ec:  add     x10, x10, #0x24            |
   0xffffffc00902d2f0:  add     sp, sp, #0x10              |    // <- destroy just current
   0xffffffc00902d2f4:  br      x10 ---------------------. |    //    BPF stack frame
   0xffffffc00902d2f8:  mov     x10, #0xfffffffffffffffc | |    //    before the tail call
   0xffffffc00902d2fc:  ldr     w7, [x25, x10]           | |
   0xffffffc00902d300:  add     sp, sp, #0x10            | |
   0xffffffc00902d304:  ldp     x27, x28, [sp], #16      | |
   0xffffffc00902d308:  ldp     x25, x26, [sp], #16      | |
   0xffffffc00902d30c:  ldp     x21, x22, [sp], #16      | |
   0xffffffc00902d310:  ldp     x19, x20, [sp], #16      | |
   0xffffffc00902d314:  ldp     x29, x30, [sp], #16      | |
   0xffffffc00902d318:  add     x0, x7, #0x0             | |
   0xffffffc00902d31c:  autiasp                          | |
   0xffffffc00902d320:  ret                              | |
                                                         | |
int classifier_0(struct __sk_buff *skb):                 | |
   0xffffffc008ff5874:  paciasp                          | |
   0xffffffc008ff5878:  stp     x29, x30, [sp, #-16]!    | |
   0xffffffc008ff587c:  mov     x29, sp                  | |
   0xffffffc008ff5880:  stp     x19, x20, [sp, #-16]!    | |
   0xffffffc008ff5884:  stp     x21, x22, [sp, #-16]!    | |
   0xffffffc008ff5888:  stp     x25, x26, [sp, #-16]!    | |
   0xffffffc008ff588c:  stp     x27, x28, [sp, #-16]!    | |
   0xffffffc008ff5890:  mov     x25, sp                  | |
   0xffffffc008ff5894:  mov     x26, #0x0                | |
   0xffffffc008ff5898:  bti     j <----------------------' |
   0xffffffc008ff589c:  sub     x27, x25, #0x0             |
   0xffffffc008ff58a0:  sub     sp, sp, #0x0               |
   0xffffffc008ff58a4:  mov     x0, #0xffffffc0ffffffff    |
   0xffffffc008ff58a8:  movk    x0, #0x8fc, lsl #16        |
   0xffffffc008ff58ac:  movk    x0, #0x6000                |
   0xffffffc008ff58b0:  mov     w1, #0x1                   |
   0xffffffc008ff58b4:  str     w1, [x0]                   |
   0xffffffc008ff58b8:  mov     w7, #0x0                   |
   0xffffffc008ff58bc:  mov     sp, sp                     |
   0xffffffc008ff58c0:  ldp     x27, x28, [sp], #16        |
   0xffffffc008ff58c4:  ldp     x25, x26, [sp], #16        |
   0xffffffc008ff58c8:  ldp     x21, x22, [sp], #16        |
   0xffffffc008ff58cc:  ldp     x19, x20, [sp], #16        |
   0xffffffc008ff58d0:  ldp     x29, x30, [sp], #16        |
   0xffffffc008ff58d4:  add     x0, x7, #0x0               |
   0xffffffc008ff58d8:  autiasp                            |
   0xffffffc008ff58dc:  ret -------------------------------'
Signed-off-by: default avatarJakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220617105735.733938-3-jakub@cloudflare.com
      d4609a5d
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