Re: [PATCHv2 for-next 1/3] RDMA/rtrs-clt: Print more info when an error happens

[Leon Romanovsky <leon@kernel.org>]

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.

> 
> We will run some benchmarks to see if it makes a difference.
> 
> Thanks
> >
> > Thanks