On Thu 17-09-20 11:03:56, Vijay Balakrishna wrote: [...] > > > The auto tuned value is incorrect post hotplug memory operation, in our use > > > case memoy hot add occurs very early during boot. > > Define incorrect. What are the actual values? Have you tried to increase > > the value manually after the hotplug? > > In our case SoC with 8GB memory, system tuned min_free_kbytes > - first to 22528 > - we perform memory hot add very early in boot What was the original and after-the-hotplug size of memory and layout? I suspect that all the hotplugged memory is in Movable zone, right? > - now min_free_kbytes is 8703 > > Before looking at code, first I manually restored min_free_kbytes soon after > boot, reran stress and didn't notice symptoms I mentioned in change log. This is really surprising and I strongly suspect that an earlier reclaim just changed the timing enough so that workload has spread the memory prpessure over a longer time and that might have been enough to recycle some of the unreclaimable memory due to its natural life time. But this is a pure speculation. Much more data would be needed to analyze this. In any case your stress test is oveprovisioning your Normal zone and increased min_free_kbytes just papers over the sizing problem. -- Michal Hocko SUSE Labs
