From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: davem@davemloft.net
Cc: daniel@iogearbox.net, andrii@kernel.org, tj@kernel.org,
memxor@gmail.com, delyank@fb.com, linux-mm@kvack.org,
bpf@vger.kernel.org, kernel-team@fb.com
Subject: [PATCH v6 bpf-next 00/16] bpf: BPF specific memory allocator.
Date: Fri, 2 Sep 2022 14:10:42 -0700 [thread overview]
Message-ID: <20220902211058.60789-1-alexei.starovoitov@gmail.com> (raw)
From: Alexei Starovoitov <ast@kernel.org>
Introduce any context BPF specific memory allocator.
Tracing BPF programs can attach to kprobe and fentry. Hence they
run in unknown context where calling plain kmalloc() might not be safe.
Front-end kmalloc() with per-cpu cache of free elements.
Refill this cache asynchronously from irq_work.
Major achievements enabled by bpf_mem_alloc:
- Dynamically allocated hash maps used to be 10 times slower than fully preallocated.
With bpf_mem_alloc and subsequent optimizations the speed of dynamic maps is equal to full prealloc.
- Tracing bpf programs can use dynamically allocated hash maps.
Potentially saving lots of memory. Typical hash map is sparsely populated.
- Sleepable bpf programs can used dynamically allocated hash maps.
v5->v6:
- Debugged the reason for selftests/bpf/test_maps ooming in a small VM that BPF CI is using.
Added patch 16 that optimizes the usage of rcu_barrier-s between bpf_mem_alloc and
hash map. It drastically improved the speed of htab destruction.
v4->v5:
- Fixed missing migrate_disable in hash tab free path (Daniel)
- Replaced impossible "memory leak" with WARN_ON_ONCE (Martin)
- Dropped sysctl kernel.bpf_force_dyn_alloc patch (Daniel)
- Added Andrii's ack
- Added new patch 15 that removes kmem_cache usage from bpf_mem_alloc.
It saves memory, speeds up map create/destroy operations
while maintains hash map update/delete performance.
v3->v4:
- fix build issue due to missing local.h on 32-bit arch
- add Kumar's ack
- proposal for next steps from Delyan:
https://lore.kernel.org/bpf/d3f76b27f4e55ec9e400ae8dcaecbb702a4932e8.camel@fb.com/
v2->v3:
- Rewrote the free_list algorithm based on discussions with Kumar. Patch 1.
- Allowed sleepable bpf progs use dynamically allocated maps. Patches 13 and 14.
- Added sysctl to force bpf_mem_alloc in hash map even if pre-alloc is
requested to reduce memory consumption. Patch 15.
- Fix: zero-fill percpu allocation
- Single rcu_barrier at the end instead of each cpu during bpf_mem_alloc destruction
v2 thread:
https://lore.kernel.org/bpf/20220817210419.95560-1-alexei.starovoitov@gmail.com/
v1->v2:
- Moved unsafe direct call_rcu() from hash map into safe place inside bpf_mem_alloc. Patches 7 and 9.
- Optimized atomic_inc/dec in hash map with percpu_counter. Patch 6.
- Tuned watermarks per allocation size. Patch 8
- Adopted this approach to per-cpu allocation. Patch 10.
- Fully converted hash map to bpf_mem_alloc. Patch 11.
- Removed tracing prog restriction on map types. Combination of all patches and final patch 12.
v1 thread:
https://lore.kernel.org/bpf/20220623003230.37497-1-alexei.starovoitov@gmail.com/
LWN article:
https://lwn.net/Articles/899274/
Future work:
- expose bpf_mem_alloc as uapi FD to be used in dynptr_alloc, kptr_alloc
- convert lru map to bpf_mem_alloc
- further cleanup htab code. Example: htab_use_raw_lock can be removed.
Alexei Starovoitov (16):
bpf: Introduce any context BPF specific memory allocator.
bpf: Convert hash map to bpf_mem_alloc.
selftests/bpf: Improve test coverage of test_maps
samples/bpf: Reduce syscall overhead in map_perf_test.
bpf: Relax the requirement to use preallocated hash maps in tracing
progs.
bpf: Optimize element count in non-preallocated hash map.
bpf: Optimize call_rcu in non-preallocated hash map.
bpf: Adjust low/high watermarks in bpf_mem_cache
bpf: Batch call_rcu callbacks instead of SLAB_TYPESAFE_BY_RCU.
bpf: Add percpu allocation support to bpf_mem_alloc.
bpf: Convert percpu hash map to per-cpu bpf_mem_alloc.
bpf: Remove tracing program restriction on map types
bpf: Prepare bpf_mem_alloc to be used by sleepable bpf programs.
bpf: Remove prealloc-only restriction for sleepable bpf programs.
bpf: Remove usage of kmem_cache from bpf_mem_cache.
bpf: Optimize rcu_barrier usage between hash map and bpf_mem_alloc.
include/linux/bpf_mem_alloc.h | 28 +
kernel/bpf/Makefile | 2 +-
kernel/bpf/hashtab.c | 138 +++--
kernel/bpf/memalloc.c | 634 ++++++++++++++++++++++
kernel/bpf/syscall.c | 5 +-
kernel/bpf/verifier.c | 52 --
samples/bpf/map_perf_test_kern.c | 44 +-
samples/bpf/map_perf_test_user.c | 2 +-
tools/testing/selftests/bpf/progs/timer.c | 11 -
tools/testing/selftests/bpf/test_maps.c | 38 +-
10 files changed, 820 insertions(+), 134 deletions(-)
create mode 100644 include/linux/bpf_mem_alloc.h
create mode 100644 kernel/bpf/memalloc.c
--
2.30.2
next reply other threads:[~2022-09-02 21:11 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-02 21:10 Alexei Starovoitov [this message]
2022-09-02 21:10 ` [PATCH v6 bpf-next 01/16] bpf: Introduce any context BPF specific memory allocator Alexei Starovoitov
2022-09-02 21:10 ` [PATCH v6 bpf-next 02/16] bpf: Convert hash map to bpf_mem_alloc Alexei Starovoitov
2022-09-02 21:10 ` [PATCH v6 bpf-next 03/16] selftests/bpf: Improve test coverage of test_maps Alexei Starovoitov
2022-09-02 21:10 ` [PATCH v6 bpf-next 04/16] samples/bpf: Reduce syscall overhead in map_perf_test Alexei Starovoitov
2022-09-02 21:10 ` [PATCH v6 bpf-next 05/16] bpf: Relax the requirement to use preallocated hash maps in tracing progs Alexei Starovoitov
2022-09-02 21:10 ` [PATCH v6 bpf-next 06/16] bpf: Optimize element count in non-preallocated hash map Alexei Starovoitov
2022-09-02 21:10 ` [PATCH v6 bpf-next 07/16] bpf: Optimize call_rcu " Alexei Starovoitov
2022-09-02 21:10 ` [PATCH v6 bpf-next 08/16] bpf: Adjust low/high watermarks in bpf_mem_cache Alexei Starovoitov
2022-09-02 21:10 ` [PATCH v6 bpf-next 09/16] bpf: Batch call_rcu callbacks instead of SLAB_TYPESAFE_BY_RCU Alexei Starovoitov
2022-09-02 21:10 ` [PATCH v6 bpf-next 10/16] bpf: Add percpu allocation support to bpf_mem_alloc Alexei Starovoitov
2022-09-02 21:10 ` [PATCH v6 bpf-next 11/16] bpf: Convert percpu hash map to per-cpu bpf_mem_alloc Alexei Starovoitov
2022-09-02 21:10 ` [PATCH v6 bpf-next 12/16] bpf: Remove tracing program restriction on map types Alexei Starovoitov
2022-09-02 21:10 ` [PATCH v6 bpf-next 13/16] bpf: Prepare bpf_mem_alloc to be used by sleepable bpf programs Alexei Starovoitov
2022-09-02 21:10 ` [PATCH v6 bpf-next 14/16] bpf: Remove prealloc-only restriction for " Alexei Starovoitov
2022-09-02 21:10 ` [PATCH v6 bpf-next 15/16] bpf: Remove usage of kmem_cache from bpf_mem_cache Alexei Starovoitov
2022-09-02 21:10 ` [PATCH v6 bpf-next 16/16] bpf: Optimize rcu_barrier usage between hash map and bpf_mem_alloc Alexei Starovoitov
2022-09-05 13:50 ` [PATCH v6 bpf-next 00/16] bpf: BPF specific memory allocator patchwork-bot+netdevbpf
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