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t=1789660441; bh=hPH6qf9tTmILRDRkSSFPngCp/v4lHSqWdSjRppjcWwA=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=PK1JV1485YMoCcTJI72m37Jd9fm5S31VtwW0gFIPi4GiOJ9d9hVaqtqb0Nj3ArSgy pG1CeBw8mSrtzjQDiCbKQF1Kg1XLF63MLu/gbuSJHt6IGXRcqQVcu2c+NotiTYb0BR 22dZ8DCIY5m9HsBkSsfQ+2lISgPJBFSoqoOhqV3AWu/RQ1/nmCdvsnjEDqNXSaO+yd oVx/WnAOz1QU9r7Lgv33Mb6Fz8qJOEelSnJhg2OVoD+fFyDpxvtxtUiQ3Cjg0Bg2ps mPIf8zBuuiCPZ0mtv5nXg7OLUTfxSgyhcPgZEJNLxJE6P14tBsa70vLnZCDmmaWOup b+Mb2BgTtToPQ== Message-ID: <248118c1-b204-4d79-97ce-1406439ed08f@kernel.org> Date: Thu, 17 Sep 2026 17:53:44 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/4] sched/numa: stop VMA scan filters from gating promotion To: Gregory Price , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, usama.arif@linux.dev, kas@kernel.org, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com, jannh@google.com, pfalcato@suse.de, osalvador@suse.de, hannes@cmpxchg.org, raghavendra.kt@amd.com References: <20260911001826.2109390-1-gourry@gourry.net> <20260916223525.65ae1628b1457a716efc298f@linux-foundation.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 98DAA18000D X-Stat-Signature: tg31dqnpd59px7ghpwoupssuhymm8qxk X-Rspam-User: X-HE-Tag: 1789660442-231831 X-HE-Meta: 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 rMSBWS2a RXlltxlpm6HAo4bkDDGXTvaSLn/QMSF9LC23fyPxwEbfEbKq6HJ4AKssBa/2WfbJY03tFbu7PjIdUZtetCA4Y9J/Gb0D+zLqhXXPpKFPJgbDXuNpzoOZTJtzH/vNqd0EafUZjlhlvFqc6T9MDWbqIFFvOZeKwZ1L225qK3tqH9xeWD832spQ+2O1UttpVTgY6tqUQO59SEs/uJowWhVEt243zcAHnWgCujANGDGvJL1Jj3ZE+Q2zz5YfMQXlM9XZjZJhJTmzlGVYIW9DFC8cZVwAeaOqUYKnCqtTwtikR3LkfciKwq9Hrz17JJU3yL8yjyC0XX02FyebB6UdMu47BA6aO7k2tcK4tx3VIYvTQnRFemBqzzHrXSaZbizNRPg9PI7di+7o0E07kT6cpCpZkOm5TCDf+US50Hk2ugCkbKEHvMO2YBRPBPrj1Mlamx7U2c5UguIBkDWs+kWymAgwjJJV8h6YSAz9Ly+OM Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/17/26 08:59, Gregory Price wrote: > On Wed, Sep 16, 2026 at 10:35:25PM -0700, Andrew Morton wrote: >> On Thu, 10 Sep 2026 20:18:22 -0400 Gregory Price wrote: >> >>> >>> Functional observation: >>> A 20 GB hash table VMA that previously remained entirely on CXL was >>> split evenly between DRAM and CXL after the changes - and tier >>> residency tracked hotness. This was previously affected by the >>> stavation issue caused by the "unaccessed VMA" filter. >> >> This seems very significant? >> >> Why cc:stable and Fixes:? Is this something which ran at these sorts >> of speeds before the offending commits? >> > > It's actually that the changes functionally broke numa balancing to the > point that it just became completely ineffective for very common use > cases. > > We only didn't notice because another bug: > https://lore.kernel.org/all/20260629163337.1264881-1-hannes@cmpxchg.org/ > > hid almost all these issues from being apparent on large workloads > (which was differently horrendous - that bug made ~70-90% of some > database workload memory ineligible for tiering) > > Once the shmem fix went in, all the starvation and filtering issues > become more apparent when the bandwidth numbers stopped making sense > (see above). > > Basically numa balancing has been broken since 2022/2023, and anyone > who has done any testing with it since then has been working off of > bad data (incomplete VMA coverage). I'll go through the patches from a MM side. I am not a big expert on kernel/sched/fair.c side of things. Would be good if someone could have a look on that. -- Cheers, David