On Tue, Nov 20, 2018 at 2:17 PM Dennis Zhou <dennis@xxxxxxxxxx> wrote: > > Hi Eddie, Vlad, and Willem, > > A few people mentioned to me that you guys were experiencing issues with > the percpu memory allocator. I saw the talk slides mention the > following two bullets: > > 1) allocation pattern makes the per cpu allocator reach a highly > fragmented state > 2) sometimes takes a long time (up to 12s) to create the PERCPU_HASH > maps at startup > > Could you guys elaborate a little more about the above? Some things > that would help: kernel version, cpu info, and a reproducer if possible? > > Also, I did some work last summer to make percpu allocation more > efficient, which went into the 4.14 kernel. Just to be sure, is that a > part of the kernel you guys are running? > > Thanks, > Dennis Hi, Dennis, Thanks a lot for reaching out and sorry for the delay in answering. I was trying to build something which shows the problem on a recent upstream kernel, but I was unable to do so until now. It seems like I can still reliably reproduce on one of our kernels, which has a lot of 'percpu: *' patches by you from 4.14, and with an internal application. Unfortunately, we haven't spent too much time on this issue, and I will have 'page in' state from a few months back. Hopefully, I'll be able to reproduce on a vanilla kernel and a simpler application, that we can publish, in the following days (after TG weekend). Thanks, Vlad
