> On 12 Apr 2021, at 19:34, Leon Romanovsky <leon@xxxxxxxxxx> 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@xxxxxxxxx> wrote:
>>>
>>> On Mon, Apr 12, 2021 at 2:41 PM Leon Romanovsky <leon@xxxxxxxxxx> 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@xxxxxxxxxx> wrote:
>>>>>>
>>>>>> On Tue, Apr 06, 2021 at 02:36:37PM +0200, Gioh Kim wrote:
>>>>>>> From: Gioh Kim <gi-oh.kim@xxxxxxxxxxxxxxx>
>>>>>>>
>>>>>>> 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@xxxxxxxxx>
>>>>>>> Signed-off-by: Jack Wang <jinpu.wang@xxxxxxxxx>
>>>>>>> ---
>>>>>>> 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
