On Thu, May 15, 2014 at 4:03 PM, Chirantan Ekbote <chirantan@xxxxxxxxxxxx> wrote: > Hi Tomasz, > > On Thu, May 15, 2014 at 3:44 PM, Doug Anderson <dianders@xxxxxxxxxxxx> wrote: >> Tomasz, >> >> On Thu, May 15, 2014 at 3:13 PM, Tomasz Figa <tomasz.figa@xxxxxxxxx> wrote: >>>> NOTE: if for some reason we need to keep the MCT around, we're >>>> definitely going to need to account for the fact that tweaking it >>>> affects the arch timer. ...and having the arch timer is really nice >>>> since: >>> >>> [Let me reorder the points below to make it easier to comment:] >>> >>>> * it's faster to access. >>>> * it is accessible from userspace for really fast access. >>> >>> Do you have some data on whether it is a significant difference, >>> especially considering real use cases? >> >> I know that Chrome makes _a lot_ of calls to gettimeofday() for >> profiling purposes, enough that it showed up on benchmarks. In fact, >> we made a change to the MCT to make accesses faster and there's a >> small mention of the benchmarking that was done at: >> >> https://chromium-review.googlesource.com/#/c/32190/ >> >> ...that change probably should be sent upstream, actually. >> >> I'll let Chirantan comment on how much faster arch timers were. >> ...and I think David Riley (also CCed now) may be able to comment on >> the benefits of userspace timers. >> > > When I profiled gettimeofday() calls, they were about 50 - 60% faster > with the arch timers compared to the mct. When I profiled gettimeofday(), the standard systems call version took about 2.5x longer than through a vDSO interface. > > - Chirantan -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
 |