Messages in this thread | | | Subject | Re: [PATCH] net: optimize cmpxchg in ip_idents_reserve | From | Eric Dumazet <> | Date | Thu, 16 Jan 2020 07:12:50 -0800 |
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On 1/16/20 4:27 AM, David Miller wrote: > From: Shaokun Zhang <zhangshaokun@hisilicon.com> > Date: Wed, 15 Jan 2020 11:23:40 +0800 > >> From: Yuqi Jin <jinyuqi@huawei.com> >> >> atomic_try_cmpxchg is called instead of atomic_cmpxchg that can reduce >> the access number of the global variable @p_id in the loop. Let's >> optimize it for performance. >> >> Cc: "David S. Miller" <davem@davemloft.net> >> Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru> >> Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org> >> Cc: Eric Dumazet <edumazet@google.com> >> Cc: Yang Guo <guoyang2@huawei.com> >> Signed-off-by: Yuqi Jin <jinyuqi@huawei.com> >> Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com> > > I doubt this makes any measurable improvement in performance. > > If you can document a specific measurable improvement under > a useful set of circumstances for real usage, then put those > details into the commit message and resubmit. > > Otherwise, I'm not applying this, sorry. >
Real difference that could be made here is to only use this cmpxchg() dance for CONFIG_UBSAN
When CONFIG_UBSAN is not set, atomic_add_return() is just fine.
(Supposedly UBSAN should not warn about that either, but this depends on compiler version)
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