Messages in this thread | | | Subject | Re: remove the last set_fs() in common code, and remove it for x86 and powerpc | From | Christophe Leroy <> | Date | Tue, 18 Aug 2020 20:23:12 +0200 |
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Le 18/08/2020 à 20:05, Christoph Hellwig a écrit : > On Tue, Aug 18, 2020 at 07:46:22PM +0200, Christophe Leroy wrote: >> I gave it a go on my powerpc mpc832x. I tested it on top of my newest >> series that reworks the 32 bits signal handlers (see >> https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=196278) with >> the microbenchmark test used is that series. >> >> With KUAP activated, on top of signal32 rework, performance is boosted as >> system time for the microbenchmark goes from 1.73s down to 1.56s, that is >> 10% quicker >> >> Surprisingly, with the kernel as is today without my signal's series, your >> series degrades performance slightly (from 2.55s to 2.64s ie 3.5% slower). >> >> >> I also observe, in both cases, a degradation on >> >> dd if=/dev/zero of=/dev/null count=1M >> >> Without your series, it runs in 5.29 seconds. >> With your series, it runs in 5.82 seconds, that is 10% more time. > > That's pretty strage, I wonder if some kernel text cache line > effects come into play here? > > The kernel access side is only used in slow path code, so it should > not make a difference, and the uaccess code is simplified and should be > (marginally) faster. > > Btw, was this with the __{get,put}_user_allowed cockup that you noticed > fixed? >
Yes it is with the __get_user_size() replaced by __get_user_size_allowed().
Christophe
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