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.
That's a surprise to me.
Just checked, min gcc requirement is 4.9[1], debian Buster is using
gcc 8.3, upcoming Bullseye will use gcc 10.2
[1]: https://www.kernel.org/doc/html/latest/process/changes.html
>
> >
> > We will run some benchmarks to see if it makes a difference.
> >
> > Thanks
> > >
> > > Thanks
