Roman Gushchin writes:
Hm, it looks a bit suspicious to me.
Let's say memory.low = 3G, memory.min = 1G and memory.current = 2G.
cgroup_size / protection == 1, so scan doesn't depend on memory.min at all.
So, we need to look directly at memory.emin in memcg_low_reclaim case, and
ignore memory.(e)low.
Hmm, this isn't really a common situation that I'd thought about, but it seems
reasonable to make the boundaries when in low reclaim to be between min and
low, rather than 0 and low. I'll add another patch with that. Thanks
+ scan = clamp(scan, SWAP_CLUSTER_MAX, lruvec_size);
Idk, how much sense does it have to make it larger than SWAP_CLUSTER_MAX,
given that it will become 0 on default (and almost any other) priority.
In my testing, setting the scan target to 0 and thus reducing scope for reclaim
can result in increasing the scan priority more than is desirable, and since we
base some vm heuristics based on that, that seemed concerning.
I'd rather start being a bit more cautious, erring on the side of scanning at
least some pages from this memcg when priority gets elevated.
Thanks for the review!
