From: Xin Long <lucien.xin@gmail.com>
To: David Laight <David.Laight@aculab.com>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>,
Neil Horman <nhorman@tuxdriver.com>,
network dev <netdev@vger.kernel.org>,
"linux-sctp@vger.kernel.org" <linux-sctp@vger.kernel.org>,
"davem@davemloft.net" <davem@davemloft.net>
Subject: Re: [PATCHv2 net-next 04/12] sctp: implement make_datafrag for sctp_stream_interleave
Date: Sat, 9 Dec 2017 01:37:14 +0800 [thread overview]
Message-ID: <CADvbK_dvEmGr9N_-qGW1gqBXZO7snxv0f8vZM2vZKYcCptqbEQ@mail.gmail.com> (raw)
In-Reply-To: <b727ce7a5f8746219987775dab5d1e1a@AcuMS.aculab.com>
On Sat, Dec 9, 2017 at 1:29 AM, David Laight <David.Laight@aculab.com> wrote:
> From: Xin Long ...
>> Hi, David, Sorry, I'm not sure we're worrying about the cpu cost or
>> codes style now ?
>>
>> For cpu cost, I think 0x848(%r13) operation must be better than the
>> generated code of if-else.
>
> Nope - the call xxx(%ryyy) is likely to be a data cache miss and a complete
> cpu pipeline stall.
>
> The conditional will be a data cache hit and the code (for one branch)
> will be prefetched and speculatively executed.
>
> Some very modern cpu might manage to predict indirect jumps, but for
> most it is a full pipeline stall.
Thanks for the CPU information.
The thing is with if-else can't avoid xxx(%ryyy) in this case, as Marcelo
said above. It seems if-else will just be a extra cost compare to this one.
next prev parent reply other threads:[~2017-12-08 17:37 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-08 13:03 [PATCHv2 net-next 00/12] sctp: Implement Stream Interleave: The I-DATA Chunk Supporting User Message Interleaving Xin Long
2017-12-08 13:03 ` [PATCHv2 net-next 01/12] sctp: add stream interleave enable members and sockopt Xin Long
2017-12-08 13:03 ` [PATCHv2 net-next 02/12] sctp: add asoc intl_enable negotiation during 4 shakehands Xin Long
2017-12-08 13:04 ` [PATCHv2 net-next 03/12] sctp: add basic structures and make chunk function for idata Xin Long
2017-12-08 13:04 ` [PATCHv2 net-next 04/12] sctp: implement make_datafrag for sctp_stream_interleave Xin Long
2017-12-08 13:04 ` [PATCHv2 net-next 05/12] sctp: implement assign_number " Xin Long
2017-12-08 13:04 ` [PATCHv2 net-next 06/12] sctp: implement validate_data " Xin Long
2017-12-08 13:04 ` [PATCHv2 net-next 07/12] sctp: implement ulpevent_data " Xin Long
2017-12-08 13:04 ` [PATCHv2 net-next 08/12] sctp: implement enqueue_event " Xin Long
2017-12-08 13:04 ` [PATCHv2 net-next 09/12] sctp: implement renege_events " Xin Long
2017-12-08 13:04 ` [PATCHv2 net-next 10/12] sctp: implement start_pd " Xin Long
2017-12-08 13:04 ` [PATCHv2 net-next 11/12] sctp: implement abort_pd " Xin Long
2017-12-08 13:04 ` [PATCHv2 net-next 12/12] sctp: add support for the process of unordered idata Xin Long
2017-12-08 14:06 ` [PATCHv2 net-next 04/12] sctp: implement make_datafrag for sctp_stream_interleave David Laight
2017-12-08 14:56 ` Marcelo Ricardo Leitner
2017-12-08 15:01 ` David Laight
2017-12-08 15:15 ` 'Marcelo Ricardo Leitner'
2017-12-08 15:32 ` David Laight
2017-12-08 16:02 ` 'Marcelo Ricardo Leitner'
2017-12-08 15:37 ` Neil Horman
2017-12-08 16:00 ` Marcelo Ricardo Leitner
2017-12-08 16:04 ` David Laight
2017-12-08 16:08 ` Neil Horman
2017-12-08 20:37 ` 'Marcelo Ricardo Leitner'
2017-12-08 16:17 ` Xin Long
2017-12-08 16:22 ` David Laight
2017-12-08 17:23 ` Xin Long
2017-12-08 17:29 ` David Laight
2017-12-08 17:37 ` Xin Long [this message]
2017-12-11 16:23 ` [PATCHv2 net-next 00/12] sctp: Implement Stream Interleave: The I-DATA Chunk Supporting User Message Interleaving David Miller
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