On Sun, Feb 06, 2022 at 02:28:18PM -0800, David Rientjes wrote: > On Fri, 4 Feb 2022, Jonghyeon Kim wrote: > > > > > This patch allows kdamond thread to select watermark options for monitoring > > > > specific node or whole system free memory. > > > > > > Why only specific NUMA node or whole system, instead of each NUMA node? Are > > > you running DARC for only specific NUMA node? If that's the case, I think > > > implementing your own DAMON-based policy in user space might be a better > > > choice. For example, you could implement and use a user-space daemon that > > > monitors free memory ratio of each NUMA node and adjusts the watermarks. > > > > > > > I have tested DAMON_RECLAIM for each NUMA node by using a module. But, I felt > > that the goal of DAMON_RECLAIM is dealing with the entire system memory or > > specific monitoring regions by using module parameters. So, I hoped to add more > > options for DAMON_RECLAIM on the NUMA system. > > > > Another thing I considered is the problem of correlation between NUMA node range > > and monitoring start/end addresses, such as "What if we monitor target that > > spans multiple nodes?". > > In that case, I guess we have to decide the policy for watermarks. > > > > > Hope I'm not making you get me wrong. You found the important limitation of > > > DAMON_RECLAIM, thank you! I really hope DAMON_RECLAIM to evolve to handle the > > > case. I'm just saying this patch looks like specialized for your special case, > > > and there could be a better approach for that. > > > > > > > If you agree that each NUMA node is able to have its own DAMON_RECLAIM daemon > > threads, I will add that codes in the next patch. > > > > It seems like one DAMON context per NUMA node is required for this, no? > Exactly, what I intend it. > In other words, since each context has its own set of memory regions that > it monitors and set of watermarks that it must abide by, if we want per > NUMA node proactive reclaim then each node must have its own context that > is coordinated by userspace if we want to do system-wide proactive > reclaim. Yes, that's why I was concerned about the correlation between the NUMA range and monitoring regions by userspace parameter. Therefore, I plan to add new parameters for per NUMA node proactive reclaim and specific monitoring target regions including system-wide proactive reclaim.
