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This preserves the > existing policy of filling available fast memory before relying on > hotness and rate-limit control. > > That is not always the desired policy. Some deployments may intentionally > keep part of a workload's memory on CXL-attached memory, for example to > preserve a desired DRAM/CXL capacity split or bandwidth distribution. With > the free-space bypass, short cold accesses and bursts of hot accesses can > refill the fast tier and pull the workload away from that distribution > whenever DRAM has free space. Currently promotion happens on 1st access. Won't it be more natural to tweak this frequency of access and also the time between successive accesses to prevent promotion due to short cold accesses and bursts of hot accesses rather than free space bypass configuration? Regards, Bharata.