On Wed, Jun 03, 2020 at 07:28:53AM -0700, Andi Kleen wrote: > > Its time cost is about 800 nanoseconds on a 2C/4T platform and > > 2~3 microseconds on a 2S/36C/72T server in normal case, and in > > worst case where vm_committed_as's spinlock is under severe > > contention, it costs 30~40 microseconds for the 2S/36C/72T sever, > > This will be likely 40-80us on larger systems, although the overhead > is often non linear so it might get worse. > > > which should be fine for its only two users: /proc/meminfo and > > HyperV balloon driver's status trace per second. > > There are some setups who do frequent sampling of /proc/meminfo > in the background. Increased overhead could be a problem for them. > But not proposing a change now. If someone complains have to > revisit I guess, perhaps adding a rate limit of some sort. Agree. Maybe I should also put the time cost info into the code comments in case someone noticed the slowdown. Thanks, Feng > > -Andi
