On Wed, May 26, 2021 at 10:30:27AM +0100, Tvrtko Ursulin wrote: > > On 25/05/2021 18:15, Matthew Brost wrote: > > On Tue, May 25, 2021 at 10:24:09AM +0100, Tvrtko Ursulin wrote: > > > > > > On 06/05/2021 20:13, Matthew Brost wrote: > > > > With the introduction of non-blocking CTBs more than one CTB can be in > > > > flight at a time. Increasing the size of the CTBs should reduce how > > > > often software hits the case where no space is available in the CTB > > > > buffer. > > > > > > I'd move this before the patch which adds the non-blocking send since that > > > one claims congestion should be rare with properly sized buffers. So it > > > makes sense to have them sized properly back before that one. > > > > > > > IMO patch ordering is a bit of bikeshed. All these CTBs changes required > > for GuC submission (34-40, 54) will get posted its own series and get > > merged together. None of the individual patches break anything or is any > > of this code really used until GuC submission is turned on. I can move > > this when I post these patches by themselves but I just don't really see > > the point either way. > > As a general principle we do try to have work in the order which makes sense > functionality wise. > > That includes trying to avoid adding and then removing, or changing a lot, > the same code within the series. And also adding functionality which is > known to not work completely well until later in the series. > > With a master switch at the end of series you can sometimes get away with > it, but if nothing else it at least makes it much easier to read if things > are flowing in the expected way within (the series). > > In this particular example sizing the buffers appropriately before starting > to use the facility a lot more certainly sounds like a no brainer to me, > especially since the patch is so trivial to move conflict wise. > Fair enough. I'll reorder these patches when I do a post to merge these ones. Matt > Regards, > > Tvrtko > > > Matt > > > Regards, > > > > > > Tvrtko > > > > > > > Cc: John Harrison <john.c.harrison@xxxxxxxxx> > > > > Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx> > > > > --- > > > > drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c | 11 ++++++++--- > > > > 1 file changed, 8 insertions(+), 3 deletions(-) > > > > > > > > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c > > > > index 77dfbc94dcc3..d6895d29ed2d 100644 > > > > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c > > > > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c > > > > @@ -63,11 +63,16 @@ static inline struct drm_device *ct_to_drm(struct intel_guc_ct *ct) > > > > * +--------+-----------------------------------------------+------+ > > > > * > > > > * Size of each `CT Buffer`_ must be multiple of 4K. > > > > - * As we don't expect too many messages, for now use minimum sizes. > > > > + * We don't expect too many messages in flight at any time, unless we are > > > > + * using the GuC submission. In that case each request requires a minimum > > > > + * 16 bytes which gives us a maximum 256 queue'd requests. Hopefully this > > > > + * enough space to avoid backpressure on the driver. We increase the size > > > > + * of the receive buffer (relative to the send) to ensure a G2H response > > > > + * CTB has a landing spot. > > > > */ > > > > #define CTB_DESC_SIZE ALIGN(sizeof(struct guc_ct_buffer_desc), SZ_2K) > > > > #define CTB_H2G_BUFFER_SIZE (SZ_4K) > > > > -#define CTB_G2H_BUFFER_SIZE (SZ_4K) > > > > +#define CTB_G2H_BUFFER_SIZE (4 * CTB_H2G_BUFFER_SIZE) > > > > #define MAX_US_STALL_CTB 1000000 > > > > @@ -753,7 +758,7 @@ static int ct_read(struct intel_guc_ct *ct, struct ct_incoming_msg **msg) > > > > /* beware of buffer wrap case */ > > > > if (unlikely(available < 0)) > > > > available += size; > > > > - CT_DEBUG(ct, "available %d (%u:%u)\n", available, head, tail); > > > > + CT_DEBUG(ct, "available %d (%u:%u:%u)\n", available, head, tail, size); > > > > GEM_BUG_ON(available < 0); > > > > header = cmds[head]; > > > >
