On Thu, Mar 10, 2016 at 03:50:13PM -0500, Johannes Weiner wrote: > When setting memory.high below usage, nothing happens until the next > charge comes along, and then it will only reclaim its own charge and > not the now potentially huge excess of the new memory.high. This can > cause groups to stay in excess of their memory.high indefinitely. > > To fix that, when shrinking memory.high, kick off a reclaim cycle that > goes after the delta. I agree that we should reclaim the high excess, but I don't think it's a good idea to do it synchronously. Currently, memory.low and memory.high knobs can be easily used by a single-threaded load manager implemented in userspace, because it doesn't need to care about potential stalls caused by writes to these files. After this change it might happen that a write to memory.high would take long, seconds perhaps, so in order to react quickly to changes in other cgroups, a load manager would have to spawn a thread per each write to memory.high, which would complicate its implementation significantly. Since, in contrast to memory.max, memory.high definition allows cgroup to breach it, I believe it would be better if we spawned an asynchronous reclaim work from the kernel on write to memory.high instead of doing this synchronously. I guess we could reuse mem_cgroup->high_work for that. Thanks, Vladimir -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
