On Fri, Dec 11, 2015 at 03:35:54PM +0000, John Harrison wrote: > On 11/12/2015 14:55, Chris Wilson wrote: > >On Fri, Dec 11, 2015 at 01:12:01PM +0000, John.C.Harrison@xxxxxxxxx wrote: > >>From: John Harrison <John.C.Harrison@xxxxxxxxx> > >> > >>The notify function can be called many times without the seqno > >>changing. A large number of duplicates are to prevent races due to the > >>requirement of not enabling interrupts until requested. However, when > >>interrupts are enabled the IRQ handle can be called multiple times > >>without the ring's seqno value changing. This patch reduces the > >>overhead of these extra calls by caching the last processed seqno > >>value and early exiting if it has not changed. > >This is just plain wrong. Every user-interrupt is preceded by a seqno > >update. > Except that mutiple interrupts can be coalesced if they occur too > close together. The driver's IRQ handler still gets called for each > individual interrupt but the first time it is run it sees the seqno > for the last. Thus all the processing gets done on the first > invocation. The multiple subsequent invocations (I have seen up to > four I believe) then have nothing to do. Yes. That is not what you implied above, or by talk about caching the seqno -- which is already cached. There is a reason why we don't do this in the interrupt handler and are not about to do so again. -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
