Re: [PATCH v2 1/2] powerpc/bug: Remove specific powerpc BUG_ON() and WARN_ON() on PPC32

2021-08-26 Thread Nicholas Piggin
Excerpts from Segher Boessenkool's message of August 27, 2021 1:30 am: > On Fri, Aug 27, 2021 at 01:04:36AM +1000, Nicholas Piggin wrote: >> Excerpts from Segher Boessenkool's message of August 27, 2021 12:37 am: >> >> No, they are all dispatched and issue to the BRU for execution. It's >> >>

Re: [PATCH v2 1/2] powerpc/bug: Remove specific powerpc BUG_ON() and WARN_ON() on PPC32

2021-08-26 Thread Segher Boessenkool
On Fri, Aug 27, 2021 at 01:04:36AM +1000, Nicholas Piggin wrote: > Excerpts from Segher Boessenkool's message of August 27, 2021 12:37 am: > >> No, they are all dispatched and issue to the BRU for execution. It's > >> trivial to construct a test of a lot of not taken branches in a row > >> and

Re: [PATCH v2 1/2] powerpc/bug: Remove specific powerpc BUG_ON() and WARN_ON() on PPC32

2021-08-26 Thread Nicholas Piggin
Excerpts from Segher Boessenkool's message of August 27, 2021 12:37 am: > On Thu, Aug 26, 2021 at 11:57:52PM +1000, Nicholas Piggin wrote: >> Excerpts from Segher Boessenkool's message of August 26, 2021 10:49 pm: >> > On Thu, Aug 26, 2021 at 01:26:14PM +1000, Nicholas Piggin wrote: >> >> Excerpts

Re: [PATCH v2 1/2] powerpc/bug: Remove specific powerpc BUG_ON() and WARN_ON() on PPC32

2021-08-26 Thread Segher Boessenkool
On Thu, Aug 26, 2021 at 11:57:52PM +1000, Nicholas Piggin wrote: > Excerpts from Segher Boessenkool's message of August 26, 2021 10:49 pm: > > On Thu, Aug 26, 2021 at 01:26:14PM +1000, Nicholas Piggin wrote: > >> Excerpts from Segher Boessenkool's message of August 19, 2021 1:06 am: > >> > On Fri,

Re: [PATCH v2 1/2] powerpc/bug: Remove specific powerpc BUG_ON() and WARN_ON() on PPC32

2021-08-26 Thread Nicholas Piggin
Excerpts from Segher Boessenkool's message of August 26, 2021 10:49 pm: > Hi! > > On Thu, Aug 26, 2021 at 01:26:14PM +1000, Nicholas Piggin wrote: >> Excerpts from Segher Boessenkool's message of August 19, 2021 1:06 am: >> > On Fri, Aug 13, 2021 at 04:08:13PM +1000, Nicholas Piggin wrote: >> >>

Re: [PATCH v2 1/2] powerpc/bug: Remove specific powerpc BUG_ON() and WARN_ON() on PPC32

2021-08-26 Thread Segher Boessenkool
Hi! On Thu, Aug 26, 2021 at 01:26:14PM +1000, Nicholas Piggin wrote: > Excerpts from Segher Boessenkool's message of August 19, 2021 1:06 am: > > On Fri, Aug 13, 2021 at 04:08:13PM +1000, Nicholas Piggin wrote: > >> This one possibly the branches end up in predictors, whereas conditional > >>

Re: [PATCH v2 1/2] powerpc/bug: Remove specific powerpc BUG_ON() and WARN_ON() on PPC32

2021-08-25 Thread Nicholas Piggin
Excerpts from Segher Boessenkool's message of August 19, 2021 1:06 am: > On Fri, Aug 13, 2021 at 04:08:13PM +1000, Nicholas Piggin wrote: >> This one possibly the branches end up in predictors, whereas conditional >> trap is always just speculated not to hit. Branches may also have a >>

Re: [PATCH v2 1/2] powerpc/bug: Remove specific powerpc BUG_ON() and WARN_ON() on PPC32

2021-08-18 Thread Segher Boessenkool
On Fri, Aug 13, 2021 at 04:08:13PM +1000, Nicholas Piggin wrote: > This one possibly the branches end up in predictors, whereas conditional > trap is always just speculated not to hit. Branches may also have a > throughput limit on execution whereas trap could be more (1 per cycle > vs 4 per

Re: [PATCH v2 1/2] powerpc/bug: Remove specific powerpc BUG_ON() and WARN_ON() on PPC32

2021-08-18 Thread Michael Ellerman
On Tue, 13 Apr 2021 16:38:09 + (UTC), Christophe Leroy wrote: > powerpc BUG_ON() and WARN_ON() are based on using twnei instruction. > > For catching simple conditions like a variable having value 0, this > is efficient because it does the test and the trap at the same time. > But most

Re: [PATCH v2 1/2] powerpc/bug: Remove specific powerpc BUG_ON() and WARN_ON() on PPC32

2021-08-13 Thread Nicholas Piggin
Excerpts from Christophe Leroy's message of April 14, 2021 2:38 am: > powerpc BUG_ON() and WARN_ON() are based on using twnei instruction. > > For catching simple conditions like a variable having value 0, this > is efficient because it does the test and the trap at the same time. > But most