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| author | Florian Westphal <fw@strlen.de> | 2016-08-12 12:03:52 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-08-14 21:12:57 -0700 |
| commit | 4cf0b354d92ee2c642532ee39e330f8f580fd985 (patch) | |
| tree | bb7716832c6e8174d1c193dcc36c432f07469939 /lib | |
| parent | 952fcfd08c8109951622579d0ae7b9cd6cafd688 (diff) | |
| download | lwn-4cf0b354d92ee2c642532ee39e330f8f580fd985.tar.gz lwn-4cf0b354d92ee2c642532ee39e330f8f580fd985.zip | |
rhashtable: avoid large lock-array allocations
Sander reports following splat after netfilter nat bysrc table got
converted to rhashtable:
swapper/0: page allocation failure: order:3, mode:0x2084020(GFP_ATOMIC|__GFP_COMP)
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.8.0-rc1 [..]
[<ffffffff811633ed>] warn_alloc_failed+0xdd/0x140
[<ffffffff811638b1>] __alloc_pages_nodemask+0x3e1/0xcf0
[<ffffffff811a72ed>] alloc_pages_current+0x8d/0x110
[<ffffffff8117cb7f>] kmalloc_order+0x1f/0x70
[<ffffffff811aec19>] __kmalloc+0x129/0x140
[<ffffffff8146d561>] bucket_table_alloc+0xc1/0x1d0
[<ffffffff8146da1d>] rhashtable_insert_rehash+0x5d/0xe0
[<ffffffff819fcfff>] nf_nat_setup_info+0x2ef/0x400
The failure happens when allocating the spinlock array.
Even with GFP_KERNEL its unlikely for such a large allocation
to succeed.
Thomas Graf pointed me at inet_ehash_locks_alloc(), so in addition
to adding NOWARN for atomic allocations this also makes the bucket-array
sizing more conservative.
In commit 095dc8e0c3686 ("tcp: fix/cleanup inet_ehash_locks_alloc()"),
Eric Dumazet says: "Budget 2 cache lines per cpu worth of 'spinlocks'".
IOW, consider size needed by a single spinlock when determining
number of locks per cpu. So with 64 byte per cacheline and 4 byte per
spinlock this gives 32 locks per cpu.
Resulting size of the lock-array (sizeof(spinlock) == 4):
cpus: 1 2 4 8 16 32 64
old: 1k 1k 4k 8k 16k 16k 16k
new: 128 256 512 1k 2k 4k 8k
8k allocation should have decent chance of success even
with GFP_ATOMIC, and should not fail with GFP_KERNEL.
With 72-byte spinlock (LOCKDEP):
cpus : 1 2
old: 9k 18k
new: ~2k ~4k
Reported-by: Sander Eikelenboom <linux@eikelenboom.it>
Suggested-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/rhashtable.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/lib/rhashtable.c b/lib/rhashtable.c index 5d845ffd7982..42acd81f10db 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -30,7 +30,7 @@ #define HASH_DEFAULT_SIZE 64UL #define HASH_MIN_SIZE 4U -#define BUCKET_LOCKS_PER_CPU 128UL +#define BUCKET_LOCKS_PER_CPU 32UL static u32 head_hashfn(struct rhashtable *ht, const struct bucket_table *tbl, @@ -70,7 +70,7 @@ static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl, unsigned int nr_pcpus = num_possible_cpus(); #endif - nr_pcpus = min_t(unsigned int, nr_pcpus, 32UL); + nr_pcpus = min_t(unsigned int, nr_pcpus, 64UL); size = roundup_pow_of_two(nr_pcpus * ht->p.locks_mul); /* Never allocate more than 0.5 locks per bucket */ @@ -83,6 +83,9 @@ static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl, tbl->locks = vmalloc(size * sizeof(spinlock_t)); else #endif + if (gfp != GFP_KERNEL) + gfp |= __GFP_NOWARN | __GFP_NORETRY; + tbl->locks = kmalloc_array(size, sizeof(spinlock_t), gfp); if (!tbl->locks) |