Hello, I have a workload, which creates lots of cache pages. Before 4.18.15, the behavior was very stable: pagecache is constantly growing until it consumes all the free memory, and then kswapd is balancing it around low watermark. After 4.18.15, once in a while khugepaged is waking up and reclaims almost all the pages from pagecache, so there is always around 2G of 8G unused. THP is enabled only for madvise case and are not used.
The exact change that leads to current behavior is https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.18.y&id=62aad93f09c1952ede86405894df1b22012fd5ab
