On Tue, 2015-03-24 at 09:56 +0530, Anshuman Khandual wrote: > On 03/24/2015 07:34 AM, Michael Ellerman wrote: > > On Fri, 2015-03-20 at 14:34 +0530, Anshuman Khandual wrote: > >> On 03/19/2015 10:13 AM, Sam Bobroff wrote: > >>> This patch changes the syscall handler to doom (tabort) active > >>> transactions when a syscall is made and return immediately without > >>> performing the syscall. > >>> > >>> Currently, the system call instruction automatically suspends an > >>> active transaction which causes side effects to persist when an active > >>> transaction fails. > >>> > >>> This does change the kernel's behaviour, but in a way that was > >>> documented as unsupported. It doesn't reduce functionality because > >>> syscalls will still be performed after tsuspend. It also provides a > >>> consistent interface and makes the behaviour of user code > >>> substantially the same across powerpc and platforms that do not > >>> support suspended transactions (e.g. x86 and s390). > >>> > >>> Performance measurements using > >>> http://ozlabs.org/~anton/junkcode/null_syscall.c > >>> indicate the cost of a system call increases by about 0.5%. > >> > >> Performance test results verified which shows an improvement of > >> around ~0.52% with the patch compared to without it. > >> > >> [With patch] null_syscall: 757.59 cycles 100.00% > >> [Without patch]] null_syscall: 753.66 cycles 100.00% > > > > No that's a performance *decrease* with the patch applied. ? > > Micheal, thats true. The cycle counts are more with patch being applied. > Here are some more results on mainline.
Right, more cycles == worse :) But it's not much more so we'll merge it. cheers _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
