Christophe Leroy's on April 7, 2020 4:18 am: > > > Le 06/04/2020 à 03:25, Nicholas Piggin a écrit : >> Christophe Leroy's on April 6, 2020 3:44 am: >>> Before : 347 cycles on null_syscall >>> After : 327 cycles on null_syscall >> >> The problem I had doing this is that signal delivery wnats full regs, >> and you don't know if you have a signal pending ahead of time if you >> have interrupts enabled. >> >> I began to try bailing out back to asm to save nvgprs and call again. >> I think that can be made to work, but it is more complication in asm, >> and I soon found that 64s CPUs don't care about NVGPRs too much so it's >> nice to get rid of the !fullregs state. > > I tried a new way in v3, please have a look. I split > syscall_exit_prepare() in 3 parts and the result is unexpected: it is > better than before the series (307 cycles now versus 311 cycles with > full ASM syscall entry/exit).
Great! Well I don't really see a problem with how you changed the C code around. I'll have to look at the assembly but I don't think it would have caused a problem for 64s. Thanks, Nick
