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author | Martynas Pumputis <m@lambda.lt> | 2019-03-18 16:10:26 +0100 |
---|---|---|
committer | Daniel Borkmann <daniel@iogearbox.net> | 2019-03-18 16:48:25 +0100 |
commit | f01a7dbe98ae4265023fa5d3af0f076f0b18a647 (patch) | |
tree | 1a3ed6ee305519403b394ceebde3c87013571f86 /kernel/bpf | |
parent | tipc: allow service ranges to be connect()'ed on RDM/DGRAM (diff) | |
download | linux-f01a7dbe98ae4265023fa5d3af0f076f0b18a647.tar.xz linux-f01a7dbe98ae4265023fa5d3af0f076f0b18a647.zip |
bpf: Try harder when allocating memory for large maps
It has been observed that sometimes a higher order memory allocation
for BPF maps fails when there is no obvious memory pressure in a system.
E.g. the map (BPF_MAP_TYPE_LRU_HASH, key=38, value=56, max_elems=524288)
could not be created due to vmalloc unable to allocate 75497472B,
when the system's memory consumption (in MB) was the following:
Total: 3942 Used: 837 (21.24%) Free: 138 Buffers: 239 Cached: 2727
Later analysis [1] by Michal Hocko showed that the vmalloc was not trying
to reclaim memory from the page cache and was failing prematurely due to
__GFP_NORETRY.
Considering dcda9b0471 ("mm, tree wide: replace __GFP_REPEAT by
__GFP_RETRY_MAYFAIL with more useful semantic") and [1], we can replace
__GFP_NORETRY with __GFP_RETRY_MAYFAIL, as it won't invoke OOM killer
and will try harder to fulfil allocation requests.
Unfortunately, replacing the body of the BPF map memory allocation
function with the kvmalloc_node helper function is not an option at
this point in time, given 1) kmalloc is non-optional for higher order
allocations, and 2) passing __GFP_RETRY_MAYFAIL to the kmalloc would
stress the slab allocator too much for large requests.
The change has been tested with the workloads mentioned above and by
observing oom_kill value from /proc/vmstat.
[1]: https://lore.kernel.org/bpf/20190310071318.GW5232@dhcp22.suse.cz/
Signed-off-by: Martynas Pumputis <m@lambda.lt>
Acked-by: Yonghong Song <yhs@fb.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20190318153940.GL8924@dhcp22.suse.cz/
Diffstat (limited to 'kernel/bpf')
-rw-r--r-- | kernel/bpf/syscall.c | 22 |
1 files changed, 15 insertions, 7 deletions
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 62f6bced3a3c..afca36f53c49 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -136,21 +136,29 @@ static struct bpf_map *find_and_alloc_map(union bpf_attr *attr) void *bpf_map_area_alloc(size_t size, int numa_node) { - /* We definitely need __GFP_NORETRY, so OOM killer doesn't - * trigger under memory pressure as we really just want to - * fail instead. + /* We really just want to fail instead of triggering OOM killer + * under memory pressure, therefore we set __GFP_NORETRY to kmalloc, + * which is used for lower order allocation requests. + * + * It has been observed that higher order allocation requests done by + * vmalloc with __GFP_NORETRY being set might fail due to not trying + * to reclaim memory from the page cache, thus we set + * __GFP_RETRY_MAYFAIL to avoid such situations. */ - const gfp_t flags = __GFP_NOWARN | __GFP_NORETRY | __GFP_ZERO; + + const gfp_t flags = __GFP_NOWARN | __GFP_ZERO; void *area; if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) { - area = kmalloc_node(size, GFP_USER | flags, numa_node); + area = kmalloc_node(size, GFP_USER | __GFP_NORETRY | flags, + numa_node); if (area != NULL) return area; } - return __vmalloc_node_flags_caller(size, numa_node, GFP_KERNEL | flags, - __builtin_return_address(0)); + return __vmalloc_node_flags_caller(size, numa_node, + GFP_KERNEL | __GFP_RETRY_MAYFAIL | + flags, __builtin_return_address(0)); } void bpf_map_area_free(void *area) |