On 9/25/20 5:31 PM, Jakub Kicinski wrote: > On Fri, 25 Sep 2020 17:15:17 +0200 Eric Dumazet wrote: >> On 9/25/20 5:00 PM, Jakub Kicinski wrote: >>> Is this_cpu_inc() in itself atomic? > > To answer my own question - it is :) > >>> unlikely((val & (COOKIE_LOCAL_BATCH - 1)) == 0)) >>> >>> Can we reasonably assume we won't have more than 4k CPUs and just >>> statically divide this space by encoding CPU id in top bits? >> >> This might give some food to side channel attacks, since this would >> give an indication of cpu that allocated the id. >> >> Also, I hear that some distros enabled 8K cpus. > > Ok :( > I was not really serious about the side channel attacks, just some thought about possible implications :) Even with 8192 max cpus, splitting space into 2^(64-13) blocks would be fine I think.
