Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to refcount_t
From: Peter Zijlstra <peterz@infradead.org>
Date: 2017-03-20 15:45:35
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bridge, lkml
On Mon, Mar 20, 2017 at 07:51:01AM -0700, Eric Dumazet wrote:
PowerPC has no efficient atomic_inc() and this definitely shows on network intensive workloads involving concurrent cores/threads.
Correct, PPC LL/SC are dreadfully expensive.
atomic_cmpxchg() on PowerPC is horribly more expensive because of the added two SYNC instructions.
Note that refcount_t uses atomic_cmpxchg_release() and atomic_cmpxchg_relaxed() which avoid most of the painful barriers.