Hello Andrew, Perhaps at this point it is best to just send a v9? : -) The v9 will include: 2 code fixlets, as suggested by Ying Huang And adding tags from both Honggyu and Ying. I just thought it would be difficult to track 4 fixlets, but please let me know whatever works best for you! Thank you always for your help. I hope you have a great day! Joshua On Mon, 5 May 2025 11:23:28 -0700 Joshua Hahn <joshua.hahnjy@xxxxxxxxx> wrote: > On machines with multiple memory nodes, interleaving page allocations > across nodes allows for better utilization of each node's bandwidth. > Previous work by Gregory Price [1] introduced weighted interleave, which > allowed for pages to be allocated across nodes according to user-set ratios. > > Ideally, these weights should be proportional to their bandwidth, so > that under bandwidth pressure, each node uses its maximal efficient > bandwidth and prevents latency from increasing exponentially. > > Previously, weighted interleave's default weights were just 1s -- which > would be equivalent to the (unweighted) interleave mempolicy, which goes > through the nodes in a round-robin fashion, ignoring bandwidth information. > > This patch has two main goals: > First, it makes weighted interleave easier to use for users who wish to > relieve bandwidth pressure when using nodes with varying bandwidth (CXL). > By providing a set of "real" default weights that just work out of the > box, users who might not have the capability (or wish to) perform > experimentation to find the most optimal weights for their system can > still take advantage of bandwidth-informed weighted interleave. > > Second, it allows for weighted interleave to dynamically adjust to > hotplugged memory with new bandwidth information. Instead of manually > updating node weights every time new bandwidth information is reported > or taken off, weighted interleave adjusts and provides a new set of > default weights for weighted interleave to use when there is a change > in bandwidth information. > > To meet these goals, this patch introduces an auto-configuration mode > for the interleave weights that provides a reasonable set of default > weights, calculated using bandwidth data reported by the system. In auto > mode, weights are dynamically adjusted based on whatever the current > bandwidth information reports (and responds to hotplug events). > > This patch still supports users manually writing weights into the nodeN > sysfs interface by entering into manual mode. When a user enters manual > mode, the system stops dynamically updating any of the node weights, > even during hotplug events that shift the optimal weight distribution. > > A new sysfs interface "auto" is introduced, which allows users to switch > between the auto (writing 1 or Y) and manual (writing 0 or N) modes. The > system also automatically enters manual mode when a nodeN interface is > manually written to. > > There is one functional change that this patch makes to the existing > weighted_interleave ABI: previously, writing 0 directly to a nodeN > interface was said to reset the weight to the system default. Before > this patch, the default for all weights were 1, which meant that writing > 0 and 1 were functionally equivalent. With this patch, writing 0 is invalid. > > [1] https://lore.kernel.org/linux-mm/20240202170238.90004-1-gregory.price@xxxxxxxxxxxx/ > > Suggested-by: Yunjeong Mun <yunjeong.mun@xxxxxx> > Suggested-by: Oscar Salvador <osalvador@xxxxxxx> > Suggested-by: Ying Huang <ying.huang@xxxxxxxxxxxxxxxxx> > Suggested-by: Harry Yoo <harry.yoo@xxxxxxxxxx> > Reviewed-by: Harry Yoo <harry.yoo@xxxxxxxxxx> > Co-developed-by: Gregory Price <gourry@xxxxxxxxxx> > Signed-off-by: Gregory Price <gourry@xxxxxxxxxx> > Signed-off-by: Joshua Hahn <joshua.hahnjy@xxxxxxxxx> > ---
