Hello, On Thu, Feb 27, 2025 at 07:54:27AM -0800, Joshua Hahn wrote: > On Thu, 27 Feb 2025 22:34:51 +0800 ying chen <yc1082463@xxxxxxxxx> wrote: > Previously, when the system is under a lot of memory pressure and is > facing OOMs, global reclaim can create space for the system and prevent > going out of memory by swapping, even when swappiness is 0. If this patch > removes that check, it would mean that global reclaim can no longer > "bypass" the swappiness == 0 condition. > > I am also CCing Johannes, who is the original author of this section [1], > who clarified in the patch that swappiness == 0 has different meanings for > global reclaim and memory cgroup reclaim. Yes. It's been the behavior for decades that swappiness is merely a preference, and that the VM *will* swap to avert OOM. You would break users making this change. If you want to hard-exempt cgroups, set memory.swap.max=0. [ Yes, it's inconsistent. But it's really cgroup_reclaim() that is the oddball in this. Also for historical reasons... ] > > when the vm.swappiness is set to 0, global reclaim should also refrain > > from memory swapping, just like these cgroups. > > > > Signed-off-by: yc1082463 <yc1082463@xxxxxxxxx> Nacked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
