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From: Haakon Bugge <haakon.bugge@oracle.com>
To: Leon Romanovsky <leon@kernel.org>
Cc: Gioh Kim <gi-oh.kim@ionos.com>, Jinpu Wang <jinpu.wang@ionos.com>,
	OFED mailing list <linux-rdma@vger.kernel.org>,
	Bart Van Assche <bvanassche@acm.org>,
	Doug Ledford <dledford@redhat.com>,
	Jason Gunthorpe <jgg@ziepe.ca>,
	Haris Iqbal <haris.iqbal@ionos.com>,
	Gioh Kim <gi-oh.kim@cloud.ionos.com>
Subject: Re: [PATCHv2 for-next 1/3] RDMA/rtrs-clt: Print more info when an error happens
Date: Tue, 13 Apr 2021 05:31:24 +0000
Message-ID: <1DFC1F4B-FF53-4AA8-B5FB-9F57B378339E@oracle.com> (raw)
In-Reply-To: <YHSErWp/Bi0kpBty@unreal>



> On 12 Apr 2021, at 19:34, Leon Romanovsky <leon@kernel.org> wrote:
> 
> On Mon, Apr 12, 2021 at 04:00:55PM +0200, Gioh Kim wrote:
>> On Mon, Apr 12, 2021 at 2:54 PM Jinpu Wang <jinpu.wang@ionos.com> wrote:
>>> 
>>> On Mon, Apr 12, 2021 at 2:41 PM Leon Romanovsky <leon@kernel.org> wrote:
>>>> 
>>>> On Mon, Apr 12, 2021 at 02:22:51PM +0200, Jinpu Wang wrote:
>>>>> On Tue, Apr 6, 2021 at 2:41 PM Leon Romanovsky <leon@kernel.org> wrote:
>>>>>> 
>>>>>> On Tue, Apr 06, 2021 at 02:36:37PM +0200, Gioh Kim wrote:
>>>>>>> From: Gioh Kim <gi-oh.kim@cloud.ionos.com>
>>>>>>> 
>>>>>>> Client prints only error value and it is not enough for debugging.
>>>>>>> 
>>>>>>> 1. When client receives an error from server:
>>>>>>> the client does not only print the error value but also
>>>>>>> more information of server connection.
>>>>>>> 
>>>>>>> 2. When client failes to send IO:
>>>>>>> the client gets an error from RDMA layer. It also
>>>>>>> print more information of server connection.
>>>>>>> 
>>>>>>> Signed-off-by: Gioh Kim <gi-oh.kim@ionos.com>
>>>>>>> Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
>>>>>>> ---
>>>>>>> drivers/infiniband/ulp/rtrs/rtrs-clt.c | 33 ++++++++++++++++++++++----
>>>>>>> 1 file changed, 29 insertions(+), 4 deletions(-)
>>>>>>> 
>>>>>>> diff --git a/drivers/infiniband/ulp/rtrs/rtrs-clt.c b/drivers/infiniband/ulp/rtrs/rtrs-clt.c
>>>>>>> index 5062328ac577..a534b2b09e13 100644
>>>>>>> --- a/drivers/infiniband/ulp/rtrs/rtrs-clt.c
>>>>>>> +++ b/drivers/infiniband/ulp/rtrs/rtrs-clt.c
>>>>>>> @@ -437,6 +437,11 @@ static void complete_rdma_req(struct rtrs_clt_io_req *req, int errno,
>>>>>>>      req->in_use = false;
>>>>>>>      req->con = NULL;
>>>>>>> 
>>>>>>> +     if (unlikely(errno)) {
>>>>>> 
>>>>>> I'm sorry, but all your patches are full of these likely/unlikely cargo
>>>>>> cult. Can you please provide supportive performance data or delete all
>>>>>> likely/unlikely in all rtrs code?
>>>>> 
>>>>> Hi Leon,
>>>>> 
>>>>> All the likely/unlikely from the non-fast path was removed as you
>>>>> suggested in the past.
>>>>> This one is on IO path, my understanding is for the fast path, with
>>>>> likely/unlikely macro,
>>>>> the compiler will optimize the code for better branch prediction.
>>>> 
>>>> In theory yes, in practice. gcc 10 generated same assembly code when I
>>>> placed likely() and replaced it with unlikely() later.
>> 
>> Even-thought gcc 10 generated the same assembly code,
>> there is no guarantee for gcc 11 or gcc 12.
>> 
>> I am reviewing rtrs source file and have found some unnecessary likely/unlikely.
>> But I think likely/unlikely are necessary for extreme cases.
>> I will have a discussion with my colleagues and inform you of the result.
> 
> Please come with performance data.

I think the best way to gather performance data is not remove the likely/unlikely, but swap their definitions. Less coding and more pronounced difference - if any.


Thxs, Håkon


  reply index

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-06 12:36 [PATCHv2 for-next 0/3] Improve debugging messages Gioh Kim
2021-04-06 12:36 ` [PATCHv2 for-next 1/3] RDMA/rtrs-clt: Print more info when an error happens Gioh Kim
2021-04-06 12:41   ` Leon Romanovsky
2021-04-09  9:57     ` Gioh Kim
2021-04-12 12:22     ` Jinpu Wang
2021-04-12 12:41       ` Leon Romanovsky
2021-04-12 12:53         ` Jinpu Wang
2021-04-12 14:00           ` Gioh Kim
2021-04-12 17:34             ` Leon Romanovsky
2021-04-13  5:31               ` Haakon Bugge [this message]
2021-04-13  6:43                 ` Leon Romanovsky
2021-04-13 13:11                   ` Gioh Kim
2021-04-13 19:31                     ` Leon Romanovsky
2021-04-13 22:52   ` Jason Gunthorpe
2021-04-06 12:36 ` [PATCHv2 for-next 2/3] RDMA/rtrs-srv: More debugging info when fail to send reply Gioh Kim
2021-04-06 12:36 ` [PATCHv2 for-next 3/3] RDMA/rtrs-clt: Simplify error message Gioh Kim
2021-04-13 22:52 ` [PATCHv2 for-next 0/3] Improve debugging messages Jason Gunthorpe

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