I just did a quick test on a patched kernel to check on that "no longer affine to..." message:
# nproc 64 # taskset -p 4 $$ pid 2261's current affinity mask: ffffffffffffffff pid 2261's new affinity mask: 4 # echo off > /sys/devices/system/cpu/cpu2/online # taskset -p $$ pid 2261's current affinity mask: fffffffffffffffb # echo on > /sys/devices/system/cpu/cpu2/online # taskset -p $$ pid 2261's current affinity mask: ffffffffffffffff # dmesg | tail -5 [ 143.996375] process 2261 (bash) no longer affine to cpu2 [ 143.996657] IRQ 114: no longer affine to CPU2 [ 144.007472] IRQ 227: no longer affine to CPU2 [ 144.013460] smpboot: CPU 2 is now offline [ 162.685519] smpboot: Booting Node 0 Processor 2 APIC 0x4 dmesg output is observably the same on patched and unpatched kernels in this case. The only difference in output is that on an unpatched kernel, the last `taskset -p $$` outputs: pid 2274's current affinity mask: fffffffffffffffb Which is the behavior that this patch aims to modify This case, which I believe is generalizable, demonstrates that we retain the "no longer affine to..." output on a kernel with this patch. Best, Joel Savitz On Thu, Jun 13, 2019 at 8:02 AM Michal Koutný <mkou...@suse.com> wrote: > > On Tue, May 28, 2019 at 02:10:37PM +0200, Michal Koutný <mkou...@suse.com> > wrote: > > Although, on v1 we will lose the "no longer affine to..." message > > (which is what happens in your demo IIUC). > FWIW, I was wrong, off by one 'state' transition. So the patch doesn't > cause change in messaging (not tested though).
