From: Alexei Starovoitov <a...@fb.com> Date: Mon, 7 Mar 2016 21:57:12 -0800
> 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.wag...@bmw-carit.de> > Reported-by: Tom Zanussi <tom.zanu...@linux.intel.com> Series applied, thanks Alexei.
