> [Felix Marti] In addition, is arming the CQ really in the performance
> path? - Don't apps poll the CQ as long as there are pending CQEs and
> only arm the CQ for notification once there is nothing left to do? If
> this is the case, it would mean that we waste a few cycles 'idle'
> cycles.
Appli
On Thu, 2007-01-04 at 07:07 +0200, Michael S. Tsirkin wrote:
> > If you think I should not add the udata parameter to the req_notify_cq()
> > provider verb, then I can rework the chelsio driver:
> >
> > 1) at cq creation time, pass the virtual address of the u32 used by the
> > library to track th
> If you think I should not add the udata parameter to the req_notify_cq()
> provider verb, then I can rework the chelsio driver:
>
> 1) at cq creation time, pass the virtual address of the u32 used by the
> library to track the current cq index. That way the chelsio kernel
> driver can save the
On Wed, 2007-01-03 at 21:33 +0200, Michael S. Tsirkin wrote:
> > Without extra param (1000 iterations in cycles):
> > ave 101.283 min 91 max 247
> > With extra param (1000 iterations in cycles):
> > ave 103.311 min 91 max 221
>
> A 2% hit then. Not huge, but 0 either.
>
> > Convert cycle
> Without extra param (1000 iterations in cycles):
> ave 101.283 min 91 max 247
> With extra param (1000 iterations in cycles):
> ave 103.311 min 91 max 221
A 2% hit then. Not huge, but 0 either.
> Convert cycles to ns (3466.727 MHz CPU):
>
> Without: 101.283 / 3466.727 = .02922us =
> > > > ib_set_cq_udata() would transition into the kernel to pass in the
> > > > consumer's index. In addition, ib_req_notify_cq would also transition
> > > > into the kernel since its not a bypass function for chelsio.
> > >
> > > We misunderstand each other.
> > >
> > > ib_uverbs_req_notify_c
> > > > No, it won't need 2 transitions - just an extra function call,
> > > > so it won't hurt performance - it would improve performance.
> > > >
> > > > ib_uverbs_req_notify_cq would call
> > > >
> > > > ib_uverbs_req_notify_cq()
> > > > {
> > > > ib_set
> > > I've run this code with mthca and didn't notice any performance
> > > degradation, but I wasn't specifically measuring cq_poll overhead in a
> > > tight loop...
> >
> > We were speaking about ib_req_notify_cq here, actually, not cq poll.
> > So what was tested?
> >
>
> Sorry, I meant req_n
On Wed, 2007-01-03 at 17:00 +0200, Michael S. Tsirkin wrote:
> > >
> > > No, it won't need 2 transitions - just an extra function call,
> > > so it won't hurt performance - it would improve performance.
> > >
> > > ib_uverbs_req_notify_cq would call
> > >
> > > ib_uverbs_req_notify_cq()
> > >
On Wed, 2007-01-03 at 17:02 +0200, Michael S. Tsirkin wrote:
> > I've run this code with mthca and didn't notice any performance
> > degradation, but I wasn't specifically measuring cq_poll overhead in a
> > tight loop...
>
> We were speaking about ib_req_notify_cq here, actually, not cq poll.
> S
> I've run this code with mthca and didn't notice any performance
> degradation, but I wasn't specifically measuring cq_poll overhead in a
> tight loop...
We were speaking about ib_req_notify_cq here, actually, not cq poll.
So what was tested?
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> >
> > No, it won't need 2 transitions - just an extra function call,
> > so it won't hurt performance - it would improve performance.
> >
> > ib_uverbs_req_notify_cq would call
> >
> > ib_uverbs_req_notify_cq()
> > {
> > ib_set_cq_udata(cq, udata)
> >
> > >
> > > It seems all Chelsio needs is to pass in a consumer index - so, how about
> > > a new
> > > entry point? Something like void set_cq_udata(struct ib_cq *cq, struct
> > > ib_udata *udata)?
> > >
> >
> > Adding a new entry point would hurt chelsio's user mode performance if
> > if the
> > > @@ -1373,7 +1374,7 @@ int ib_peek_cq(struct ib_cq *cq, int wc_
> > > static inline int ib_req_notify_cq(struct ib_cq *cq,
> > > enum ib_cq_notify cq_notify)
> > > {
> > > - return cq->device->req_notify_cq(cq, cq_notify);
> > > + return cq->device->req_notify_cq
> > @@ -1373,7 +1374,7 @@ int ib_peek_cq(struct ib_cq *cq, int wc_
> > static inline int ib_req_notify_cq(struct ib_cq *cq,
> >enum ib_cq_notify cq_notify)
> > {
> > - return cq->device->req_notify_cq(cq, cq_notify);
> > + return cq->device->req_notify_cq(cq, c
> diff --git a/drivers/infiniband/hw/mthca/mthca_cq.c
> b/drivers/infiniband/hw/mthca/mthca_cq.c
> index 283d50b..15cbd49 100644
> --- a/drivers/infiniband/hw/mthca/mthca_cq.c
> +++ b/drivers/infiniband/hw/mthca/mthca_cq.c
> @@ -722,7 +722,8 @@ repoll:
> return err == 0 || err == -EAGAIN ? n
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