On Mon, Oct 14, 2024 at 4:25 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Mon, 14 Oct 2024 22:12:11 +0000 Wei Xu <weixugc@xxxxxxxxxx> wrote: > > > lru_gen_shrink_node() unconditionally clears kswapd_failures, which > > can prevent kswapd from sleeping and cause 100% kswapd cpu usage even > > when kswapd repeatedly fails to make progress in reclaim. > > > > Only clear kswap_failures in lru_gen_shrink_node() if reclaim makes > > some progress, similar to shrink_node(). > > That sounds bad. What triggers this? Can you suggest why it has just > bee discovered, after 1.5 years? And should the fix be backported into > -stable kernels? > I happened to run into this problem in one of my tests recently. It requires a combination of several conditions: The allocator needs to allocate a right amount of pages such that it can wake up kswapd without itself being OOM killed; there is no memory for kswapd to reclaim (My test disables swap and cleans page cache first); no other process frees enough memory at the same time. I think the fix is a good candidate for stable kernels.
