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author | Hou Tao <houtao1@huawei.com> | 2023-09-28 13:15:58 +0300 |
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committer | Alexei Starovoitov <ast@kernel.org> | 2023-09-30 19:39:28 +0300 |
commit | 9077fc228f09c9f975c498c55f5d2e882cd0da59 (patch) | |
tree | 0c0d572e4a039931672948678ebb10bd833e9db4 /kernel/bpf | |
parent | d1a783daa443d34e2f39811573ac9cbb5e5b78f3 (diff) | |
download | linux-9077fc228f09c9f975c498c55f5d2e882cd0da59.tar.xz |
bpf: Use kmalloc_size_roundup() to adjust size_index
Commit d52b59315bf5 ("bpf: Adjust size_index according to the value of
KMALLOC_MIN_SIZE") uses KMALLOC_MIN_SIZE to adjust size_index, but as
reported by Nathan, the adjustment is not enough, because
__kmalloc_minalign() also decides the minimal alignment of slab object
as shown in new_kmalloc_cache() and its value may be greater than
KMALLOC_MIN_SIZE (e.g., 64 bytes vs 8 bytes under a riscv QEMU VM).
Instead of invoking __kmalloc_minalign() in bpf subsystem to find the
maximal alignment, just using kmalloc_size_roundup() directly to get the
corresponding slab object size for each allocation size. If these two
sizes are unmatched, adjust size_index to select a bpf_mem_cache with
unit_size equal to the object_size of the underlying slab cache for the
allocation size.
Fixes: 822fb26bdb55 ("bpf: Add a hint to allocated objects.")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Closes: https://lore.kernel.org/bpf/20230914181407.GA1000274@dev-arch.thelio-3990X/
Signed-off-by: Hou Tao <houtao1@huawei.com>
Tested-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Link: https://lore.kernel.org/r/20230928101558.2594068-1-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf')
-rw-r--r-- | kernel/bpf/memalloc.c | 44 |
1 files changed, 19 insertions, 25 deletions
diff --git a/kernel/bpf/memalloc.c b/kernel/bpf/memalloc.c index cf1941516643..d93ddac283d4 100644 --- a/kernel/bpf/memalloc.c +++ b/kernel/bpf/memalloc.c @@ -965,37 +965,31 @@ void notrace *bpf_mem_cache_alloc_flags(struct bpf_mem_alloc *ma, gfp_t flags) return !ret ? NULL : ret + LLIST_NODE_SZ; } -/* Most of the logic is taken from setup_kmalloc_cache_index_table() */ static __init int bpf_mem_cache_adjust_size(void) { - unsigned int size, index; + unsigned int size; - /* Normally KMALLOC_MIN_SIZE is 8-bytes, but it can be - * up-to 256-bytes. + /* Adjusting the indexes in size_index() according to the object_size + * of underlying slab cache, so bpf_mem_alloc() will select a + * bpf_mem_cache with unit_size equal to the object_size of + * the underlying slab cache. + * + * The maximal value of KMALLOC_MIN_SIZE and __kmalloc_minalign() is + * 256-bytes, so only do adjustment for [8-bytes, 192-bytes]. */ - size = KMALLOC_MIN_SIZE; - if (size <= 192) - index = size_index[(size - 1) / 8]; - else - index = fls(size - 1) - 1; - for (size = 8; size < KMALLOC_MIN_SIZE && size <= 192; size += 8) - size_index[(size - 1) / 8] = index; + for (size = 192; size >= 8; size -= 8) { + unsigned int kmalloc_size, index; - /* The minimal alignment is 64-bytes, so disable 96-bytes cache and - * use 128-bytes cache instead. - */ - if (KMALLOC_MIN_SIZE >= 64) { - index = size_index[(128 - 1) / 8]; - for (size = 64 + 8; size <= 96; size += 8) - size_index[(size - 1) / 8] = index; - } + kmalloc_size = kmalloc_size_roundup(size); + if (kmalloc_size == size) + continue; - /* The minimal alignment is 128-bytes, so disable 192-bytes cache and - * use 256-bytes cache instead. - */ - if (KMALLOC_MIN_SIZE >= 128) { - index = fls(256 - 1) - 1; - for (size = 128 + 8; size <= 192; size += 8) + if (kmalloc_size <= 192) + index = size_index[(kmalloc_size - 1) / 8]; + else + index = fls(kmalloc_size - 1) - 1; + /* Only overwrite if necessary */ + if (size_index[(size - 1) / 8] != index) size_index[(size - 1) / 8] = index; } |