Merge branch 'bpf-map-prealloc'
Alexei Starovoitov says: ==================== bpf: map pre-alloc v1->v2: . fix few issues spotted by Daniel . converted stackmap into pre-allocation as well . added a workaround for lockdep false positive . added pcpu_freelist_populate to be used by hashmap and stackmap this path set switches bpf hash map to use pre-allocation by default and introduces BPF_F_NO_PREALLOC flag to keep old behavior for cases where full map pre-allocation is too memory expensive. Some time back Daniel Wagner reported crashes when bpf hash map is used to compute time intervals between preempt_disable->preempt_enable and recently Tom Zanussi reported a dead lock in iovisor/bcc/funccount tool if it's used to count the number of invocations of kernel '*spin*' functions. Both problems are due to the recursive use of slub and can only be solved by pre-allocating all map elements. A lot of different solutions were considered. Many implemented, but at the end pre-allocation seems to be the only feasible answer. As far as pre-allocation goes it also was implemented 4 different ways: - simple free-list with single lock - percpu_ida with optimizations - blk-mq-tag variant customized for bpf use case - percpu_freelist For bpf style of alloc/free patterns percpu_freelist is the best and implemented in this patch set. Detailed performance numbers in patch 3. Patch 2 introduces percpu_freelist Patch 1 fixes simple deadlocks due to missing recursion checks Patch 5: converts stackmap to pre-allocation Patches 6-9: prepare test infra Patch 10: stress test for hash map infra. It attaches to spin_lock functions and bpf_map_update/delete are called from different contexts Patch 11: stress for bpf_get_stackid Patch 12: map performance test Reported-by:Daniel Wagner <daniel.wagner@bmw-carit.de> Reported-by:
Tom Zanussi <tom.zanussi@linux.intel.com> ==================== Signed-off-by:
David S. Miller <davem@davemloft.net>
Please register or sign in to comment