Hi SeongJae,
On Thu, 13 Jun 2024 10:46:04 -0700 SeongJae Park <s...@kernel.org> wrote:
> Hi Honggyu,
>
> On Thu, 13 Jun 2024 22:20:47 +0900 Honggyu Kim <honggyu....@sk.com> wrote:
>
> > There was an RFC IDEA "DAMOS-based Tiered-Memory Management" previously
> > posted at [1].
> >
> > It says there is no implementation of the demote/promote DAMOS action
> > are made. This patch series is about its implementation for physical
> > address space so that this scheme can be applied in system wide level.
> >
> > Changes from RFC v4:
> > https://lore.kernel.org/20240512175447.75943-1...@kernel.org
> > 1. Add usage and design documents
> > 2. Rename alloc_demote_folio to alloc_migrate_folio
> > 3. Add evaluation results with "demotion_enabled" true
> > 4. Rebase based on v6.10-rc3
>
> I left comments on the new patches for the documentation.
>
> [...]
> >
> > Evaluation Results
> > ==================
> >
> > All the result values are normalized to DRAM-only execution time because
> > the workload cannot be faster than DRAM-only unless the workload hits
> > the peak bandwidth but our redis test doesn't go beyond the bandwidth
> > limit.
> >
> > So the DRAM-only execution time is the ideal result without affected by
> > the gap between DRAM and CXL performance difference. The NUMA node
> > environment is as follows.
> >
> > node0 - local DRAM, 512GB with a CPU socket (fast tier)
> > node1 - disabled
> > node2 - CXL DRAM, 96GB, no CPU attached (slow tier)
> >
> > The following is the result of generating zipfian distribution to
> > redis-server and the numbers are averaged by 50 times of execution.
> >
> > 1. YCSB zipfian distribution read only workload
> > memory pressure with cold memory on node0 with 512GB of local DRAM.
> >
> > ====================+================================================+=========
> > | cold memory occupied by mmap and memset |
> > | 0G 440G 450G 460G 470G 480G 490G 500G |
> >
> > ====================+================================================+=========
> > Execution time normalized to DRAM-only values |
> > GEOMEAN
> >
> > --------------------+------------------------------------------------+---------
> > DRAM-only | 1.00 - - - - - - - |
> > 1.00
> > CXL-only | 1.19 - - - - - - - |
> > 1.19
> > default | - 1.00 1.05 1.08 1.12 1.14 1.18 1.18 |
> > 1.11
> > DAMON tiered | - 1.03 1.03 1.03 1.03 1.03 1.07 *1.05 |
> > 1.04
> > DAMON lazy | - 1.04 1.03 1.04 1.05 1.06 1.06 *1.06 |
> > 1.05
> >
> > ====================+================================================+=========
> > CXL usage of redis-server in GB |
> > AVERAGE
> >
> > --------------------+------------------------------------------------+---------
> > DRAM-only | 0.0 - - - - - - - |
> > 0.0
> > CXL-only | 51.4 - - - - - - - |
> > 51.4
> > default | - 0.6 10.6 20.5 30.5 40.5 47.6 50.4 |
> > 28.7
> > DAMON tiered | - 0.6 0.5 0.4 0.7 0.8 7.1 5.6 |
> > 2.2
> > DAMON lazy | - 0.5 3.0 4.5 5.4 6.4 9.4 9.1 |
> > 5.5
> >
> > ====================+================================================+=========
> >
> > Each test result is based on the exeuction environment as follows.
>
> Nit. s/exeuction/execution/
Thanks. Fixed it.
> [...]
> > In summary, the evaluation results show that DAMON memory management
> > with DAMOS_MIGRATE_{HOT,COLD} actions reduces the performance slowdown
> > compared to the "default" memory policy from 11% to 3~5% when the system
> > runs with high memory pressure on its fast tier DRAM nodes.
> >
> > Having these DAMOS_MIGRATE_HOT and DAMOS_MIGRATE_COLD actions can make
> > tiered memory systems run more efficiently under high memory pressures.
>
> Thank you very much for continuing this great work.
>
> Other than trivial comments on documentation patches and the above typo, I
> have
> no particular concern on this patchset. I'm looking forward to the next
> version.
I have addressed all your comments and resent v6 again. Please have a
look again.
https://lore.kernel.org/20240614030010.751-1-honggyu....@sk.com
Thanks very much for your review!
Thanks,
Honggyu
>
> Thanks,
> SJ
> [...]
