From: David S. Miller <davem@davemloft.net>
Date: Tue, 29 Dec 2015 20:13:45 +0000 (-0500)
Subject: Merge branch 'bpf_hash-locking'
X-Git-Tag: v4.5-rc1~128^2~88
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=5e7112590e7cd20f2a243c51ecd9016feb319996;p=karo-tx-linux.git

Merge branch 'bpf_hash-locking'

Ming Lei says:

====================
bpf: hash: use per-bucket spinlock

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

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

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: 1184K IOPS
        - without running eBPF prog: 1492K IOPS

TODO:
        - remove the per-hashtable atomic counter

V2:
        - fix checking on buckets size
V1:
        - fix the wrong 3/3 patch
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
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5e7112590e7cd20f2a243c51ecd9016feb319996