On Wed, Nov 8, 2023 at 6:41 PM Chris Li <chrisl@xxxxxxxxxx> wrote: > > Hi Nhant, > > On Fri, Nov 3, 2023 at 12:24 PM Nhat Pham <nphamcs@xxxxxxxxx> wrote: > > > > > > Would it be more convenient if the initial value is inherited from the > > > parent (the root starts with true)? > > > > > > I can see this being useful if we want to set it to false on the > > > entire machine or one a parent cgroup, we can set it before creating > > > any children instead of setting it to 0 every time we create a new > > > cgroup. > > > > I'm not 100% sure about the benefit or have a strong opinion one way > > or another, but this sounds like a nice-to-have detail to me, and a relatively > > low cost one (both in effort and at runtime) at that too. > > > > Propagating the change everytime we modify the memory.zswap.writeback > > value of the ancestor might be data race-prone (and costly, depending on > > how big the cgroup subtree is), but this is just a one-time-per-cgroup > > propagation (at the new cgroup creation time). > > I think Yosary was suggesting inheriting the initial value from > parents. That is just one level look up when you create the new > cgroup, using the parent value as default. No recursive. > What you described above seems different to me. I understand what you > are suggesting is that writing to the parent cgroup will recursively > write to all child cgroup. > > > > Can anyone come up with a failure case for this change, or why it might be > > a bad idea? > > I would suggest against recursive changing value behavior. > What if you want the parent but also want the child to keep its value > not changed? Every change to the parent will have to go through the > child to flip it back. > Inherit from the parent seems fine. > > Chris Hi Chris, I've actually sent out a new version of the patch series implementing (what I believed to be) Yosry's suggestion. Feel free to take a look! https://lore.kernel.org/all/20231106231158.380730-1-nphamcs@xxxxxxxxx/ Here, I was actually agreeing with you - recursive propagation would not be a good idea. Best, Nhat
