>> Would you like to check run time consequences >> for the shown error code settings once more? > > Sure, lets for now ignore the fact that the performance of an error path > does not matter most of the time. I am concerned that extra error code settings within the “success path” could influence the run time behaviour in unwanted ways. > After tree building and optimization your change should not matter at all > regarding performance for a decent compiler. I find your optimism interesting. > The compiler can and will do much more complex transformations than this. This technology is often fine. > Since you have send several patches that trigger compile time warnings or > errors, let me do this exercise for you and let us check what your patch > changes in terms of run time consequences. > > > $ git checkout v4.10-rc4 > HEAD is now at 49def18... Linux 4.10-rc4 > > $ make arch/s390/kvm/kvm-s390.o > [..] Thanks for your build demonstration. > $ objdump -d arch/s390/kvm/kvm-s390.o | md5sum > 55c1e081f55cef90b3ffcc06a13721c1 - > > $ git am ~/code/elfring/[PATCH] KVM: s390: Move two error code assignments in kvm_vm_ioctl_get_dirty_log().eml > Applying: KVM: s390: Move two error code assignments in kvm_vm_ioctl_get_dirty_log() > > $ make arch/s390/kvm/kvm-s390.o > [..] > > $ objdump -d arch/s390/kvm/kvm-s390.o | md5sum > 55c1e081f55cef90b3ffcc06a13721c1 - > > As you can see the binary is identical, The hashes became the same with the selected tool. > so I can make an educated guess, that there is no performance improvement > due to your patch. How much does such a software generation result fit really to expectations? Should the two shown implementation variants for a function like "kvm_vm_ioctl_get_dirty_log" usually lead to different object code files? Regards, Markus
