Messages in this thread | | | Date | Wed, 8 Jun 2022 13:49:16 +0530 | Subject | Re: [PATCH v5 4/9] mm/demotion: Build demotion targets based on explicit memory tiers | From | Aneesh Kumar K V <> |
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On 6/8/22 12:20 PM, Ying Huang wrote: > On Fri, 2022-06-03 at 19:12 +0530, Aneesh Kumar K.V wrote: >> This patch switch the demotion target building logic to use memory tiers >> instead of NUMA distance. All N_MEMORY NUMA nodes will be placed in the >> default tier 1 and additional memory tiers will be added by drivers like >> dax kmem. >> >> This patch builds the demotion target for a NUMA node by looking at all >> memory tiers below the tier to which the NUMA node belongs. The closest node >> in the immediately following memory tier is used as a demotion target. >> >> Since we are now only building demotion target for N_MEMORY NUMA nodes >> the CPU hotplug calls are removed in this patch. >> >> The rank approach allows us to keep memory tier device IDs stable even if there >> is a need to change the tier ordering among different memory tiers. e.g. DRAM >> nodes with CPUs will always be on memtier1, no matter how many tiers are higher >> or lower than these nodes. A new memory tier can be inserted into the tier >> hierarchy for a new set of nodes without affecting the node assignment of any >> existing memtier, provided that there is enough gap in the rank values for the >> new memtier. >> >> The absolute value of "rank" of a memtier doesn't necessarily carry any meaning. >> Its value relative to other memtiers decides the level of this memtier in the tier >> hierarchy. >> >> For now, This patch supports hardcoded rank values which are 300, 200, & 100 for >> memory tiers 0,1 & 2 respectively. >> >> Below is the sysfs interface to read the rank values of memory tier, >> /sys/devices/system/memtier/memtierN/rank >> >> This interface is read only for now. Write support can be added when there is >> a need of flexibility of more number of memory tiers(> 3) with flexibile ordering >> requirement among them. >> >> Suggested-by: Wei Xu <weixugc@google.com> >> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> >> --- >> include/linux/memory-tiers.h | 5 + >> include/linux/migrate.h | 13 -- >> mm/memory-tiers.c | 269 ++++++++++++++++++++++++ >> mm/migrate.c | 394 ----------------------------------- >> mm/vmstat.c | 4 - >> 5 files changed, 274 insertions(+), 411 deletions(-) > > It appears that you moved some code from migrate.c to memory-tiers.c and > change them. If so, please separate the change. That is, one patch > only move the code, the other change the code. This will make it easier > to find out what is changed.
That was how it was done in earlier version. That is we did change establish_migration within the same file. The changes we are doing here was so different that it was mentioned that it gets very hard to review in a context diff. Hence this patch where we killed the old code and did the new code in memory-tiers.c. I could still move the code to memory-tiers.c and do the changes on top of that. Infact I do have a patch that does similar code movement in the series. But the diff was not useful for an easy review.
-aneesh
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