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b=c9C/JA8keNo5dB5zBrxnSwiYNiGwKRHlCouM0r7PngXbLQH2FoyYSC8tRczvSY3R0 PVspcWf1Ycx6P+wfrr4p0wGamBWB0lWFFNd989WSY2twUlrBSFtmjHPI+oVmvTWlvx tz40Qo62xTmHblU0sQPS1lrrX3gCeGRrbMNEpbFlW8+T5q+B4B8HQs62Iducm/NLgC PJImODa93xoCDabAOZ/WWydx69edleVhwND6Wmh/jHwtj+MuKiHdkLGxusgC3qyg6g lwHxjy3gx3WibprScbsJa9hD73qxwixYNmqEGCCIXi4GloXsDFwTKo+1TEl1sCY8Q/ d5Tn9mdcEMWxA== From: SeongJae Park To: Ravi Jonnalagadda Cc: SeongJae Park , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, akpm@linux-foundation.org, corbet@lwn.net, bijan311@gmail.com, ajayjoshi@micron.com, honggyu.kim@sk.com, yunjeong.mun@sk.com Subject: Re: [RFC PATCH v3 0/4] mm/damon: Introduce node_eligible_mem_bp and node_ineligible_mem_bp Quota Goal Metrics Date: Wed, 25 Feb 2026 16:52:46 -0800 Message-ID: <20260226005248.7509-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: bnfajudug8oekqwnxxeso6yexsdujnuz X-Rspamd-Server: rspam11 X-Rspam-User: X-Rspamd-Queue-Id: EDB1014000F X-HE-Tag: 1772067170-551177 X-HE-Meta: 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 oIjs6f5y Mp7Bnnfs1lKpASZx/8twmScpIYPBVMVKM7Uh0VllRgptfwRaEdolwVuhVKQh3ox5AXUwVU4p2FdgyAeuQVIt8CL8x4JnfZO66CntO07L+K/WtPlVn8x+3uEN1TKpMHtnJI9pax0uTZXKIY1GByDDEg47b0iT2b4kaH6IUbHm0w2vEPRYCdptcL8/fs22Z3/XqUOSaLA112hsxRfKhLRFsg/vSHCWTI7SKrfQU8PuEj6k9ytjGneCBbqX4As8vYgIK5gMVvdQ6q5hH/q7KMmxfABuLZZVBZ39D9ER/vL9luws2EgdYh8ZLZ0YUaHcncJcmHsXI5V6oCd+GWQZWpjvwzsn/99+tB6f0lGfh3BEaYfWmwSBm/3hhoBOE2raeuViyV330XwdFQ2IoobNmwHc+5lv/q0HjUJxKmxac Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, 25 Feb 2026 10:19:11 -0800 Ravi Jonnalagadda wrote: > On Mon, Feb 23, 2026 at 9:36 PM SeongJae Park wrote: > > > > Hello Ravi, > > > > On Mon, 23 Feb 2026 12:32:28 +0000 Ravi Jonnalagadda wrote: > > > > > MIME-Version: 1.0 > > > Content-Type: text/plain; charset=UTF-8 > > > Content-Transfer-Encoding: 8bit > > > > > > This series introduces two new DAMON quota goal metrics for controlling > > > memory migration in heterogeneous memory systems (e.g., DRAM and CXL > > > memory tiering) using physical address (PA) mode monitoring. > > > > Thank you for keep working on and sharing this :) > > Thank you for the detailed review! My pleasure! [...] > > > - Added PA-mode detection lag compensation cache (see dedicated section > > > below for design details). > > > > I'm not very sure if this is really needed, though. I'll leave comment on the > > dedicated section below. > > Understood. I consciously separated the cache implementation (patch 4) > from the core metrics (patch 3) because the cache is ONE possible approach to > handle detection lag - not necessarily THE approach. My goal was to share > what was needed to achieve equilibrium with my synthetic benchmark > workload (multiload), > while making it clear that the cache mechanism could be dropped or > replaced with alternatives. That was indeed helpful for reviewing, thank you! > > > > > > > > > - Added fix for esz=0 quota bypass that allowed unlimited migration when > > > goal was achieved. > > > > > > - Added fix for goal_tuner sysfs setting being ignored due to > > > damon_new_scheme() always defaulting to CONSIST. > > > > Thank you for finding and fixing these issues in my previously shared RFC patch > > series! I left a few comments to the patches. In short, the second fix looks > > good and I will add that to the next revision of my RFC patch series, if you > > don't mind. For the first fix, I'd like to take more time on thinking more > > cleaner solution. > > Sounds good. Please go ahead and incorporate the goal_tuner fix into > your series. > Happy to test whatever approach you come up with for the esz=0 issue. Thank you, I will do! [...] > > > In PA-mode, when pages are migrated: > > > 1. Source node detection drops immediately (pages are gone) > > > 2. Target node detection increases slowly (new addresses need sampling) > > > > I agree. And this is not what I clearly expected during the previous > > discussion. Thank you for sharing this issue. > > I'm glad this observation is useful. It was something I discovered during > testing that wasn't obvious until I looked at the trace data closely. Thank you for sharing the pain point. I recently added a few more DAMOS tracepoints motivated by our offline discussion. I'm planning to add better supports of those in DAMON user-space tool. Knowing this kind of pain points is essential and useful at improving DAMON, thank you! [...] > > I will leave more comments to the patch implementing this. But this seems too > > much at the current stage, unless there are clear test results showing its > > needs. I'd recommend proceeding without this, and later revisit if the problem > > becomes clearly significant. > > I agree. Let's drop patch 4 for now and focus on getting the core > metrics merged. > The cache mechanism can be revisited later if real-world usage shows > it's needed. Thank you for flexibly accepting my suggestion! [...] > > I'm yet to further reply to the fourth patch, but I hope my comments be worthy > > :) > > > > Very much so! Your feedback has been invaluable in shaping this work. :-) More than exciting to hear that :D > > I'm currently on a break and will be back after March 10th. Once I return, > I'll send the updated patch 3 and share test results with CONSIST > tuner. Sounds perfect, I hope you to have great break! Thanks, SJ [...]