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[PATCH 0/6] bpf: hash: optimization

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Hi,

This patchset tries to optimize ebpf hash map, and follows
the ideas:

1) Both htab_map_update_elem() and htab_map_delete_elem()
can be called from eBPF program, and they may be in kernel
hot path, so it isn't efficient to use a per-hashtable lock
in this two helpers, so this patch converts the lock into
per-bucket bit spinlock.

2) kmalloc() is called in htab_map_update_elem() for allocating
element, together with one global counter for tracking how many
elementes have been allocated. kmalloc is often a bit slow,
and the global counter doesn't scale well. This patch pre-allocates
one element pool and uses percpu ida for runtime element allocation/free,
and the global counter is removed too with this approach.

With this patchset, looks the performance penalty from eBPF
decreased a lot, see the following test:

1) run 'tools/biolatency' of bcc before running block test;

2) run fio to test block throught over /dev/nullb0,
(randread, 16jobs, libaio, 4k bs) and the test box
is one 24cores(dual sockets) VM server:

	- without patchset:  607K IOPS
	- with this patchset: 1332K IOPS
	- without running eBPF prog: 1492K IOPS

 include/linux/rculist.h |  55 +++++++++++
 kernel/bpf/hashtab.c    | 247 ++++++++++++++++++++++++++++++++++++++----------
 2 files changed, 252 insertions(+), 50 deletions(-)


Thanks,
Ming 

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[PATCH 0/6] bpf: hash: optimization Ming Lei <tom.leiming@gmail.com> - 2015-12-15 12:30 +0100
  [PATCH 6/6] bpf: hash: reorganize 'struct htab_elem' Ming Lei <tom.leiming@gmail.com> - 2015-12-15 12:30 +0100
  [PATCH 5/6] bpf: hash: avoid to call kmalloc() in eBPF prog Ming Lei <tom.leiming@gmail.com> - 2015-12-15 12:30 +0100
    Re: [PATCH 5/6] bpf: hash: avoid to call kmalloc() in eBPF prog Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2015-12-16 00:20 +0100
      Re: [PATCH 5/6] bpf: hash: avoid to call kmalloc() in eBPF prog Daniel Borkmann <daniel@iogearbox.net> - 2015-12-16 00:50 +0100
      Re: [PATCH 5/6] bpf: hash: avoid to call kmalloc() in eBPF prog Ming Lei <tom.leiming@gmail.com> - 2015-12-16 08:20 +0100
    Re: [PATCH 5/6] bpf: hash: avoid to call kmalloc() in eBPF prog Daniel Borkmann <daniel@iogearbox.net> - 2015-12-16 00:30 +0100
    Re: [PATCH 5/6] bpf: hash: avoid to call kmalloc() in eBPF prog Daniel Borkmann <daniel@iogearbox.net> - 2015-12-16 00:40 +0100
      Re: [PATCH 5/6] bpf: hash: avoid to call kmalloc() in eBPF prog Daniel Borkmann <daniel@iogearbox.net> - 2015-12-16 01:20 +0100
  [PATCH 2/6] hlist: prepare for supporting bit spinlock Ming Lei <tom.leiming@gmail.com> - 2015-12-15 12:30 +0100
  [PATCH 1/6] bpf: hash: use atomic count Ming Lei <tom.leiming@gmail.com> - 2015-12-15 12:30 +0100
  [PATCH 3/6] bpf: hash: move select_bucket() out of htab's spinlock Ming Lei <tom.leiming@gmail.com> - 2015-12-15 12:30 +0100

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