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AJvYcCWv2rPTOumoIx45Linoj03Zaq61wL9GKaOaYcRkJL46q1ZiRH80OzEZMX1ZkRAakSRyFXZojVsW0g==@kvack.org X-Gm-Message-State: AOJu0YzKbW+f9PH9aKourfnEjOPebsmpxDB4F/JRpW5FsO7DqR4he5dh A0qh8BUy0EgnzwztdO9O+jnJLacxz9/LUZIR4A7Xp2xhWwN3eWBq+BN6s0PHH/8UaUPxAHyOVc0 Ii/0f2XI2/kYe+3aNgg8TjznN0/sGjQORFDJpwU0= X-Gm-Gg: ASbGnct2RcJM6MCNvmb0lxneLb1h3OciQe9hzPSUa4UpH5fYvGV85Lsp6AGantz8JxV +BLzbQQMoYAMkrfzCbEJ+ZiwuHELk45ioWUGTLPkB/+euppryw7oOxjOJBQRho0n79lBpBZcXnC 3d1hGhIn4HppH6fBc8dKB9Sw2TM9v2U3R6Nvahyfhysk04v/GC0xyvcQtFILo7/5A69Z2H8Pa8X eJQpA== X-Google-Smtp-Source: AGHT+IF53yd5TzJjggB8GCsgXjHW3XfBe88y6aXb2DUIoaNxkcU59GbTifghsdJkMCaNQP84ylFD8Fm+lkPnJG8ON1s= X-Received: by 2002:a17:907:1ca6:b0:ae0:9fce:c578 with SMTP id a640c23a62f3a-ae09fcedefcmr284922166b.18.1750720891641; Mon, 23 Jun 2025 16:21:31 -0700 (PDT) MIME-Version: 1.0 References: <20250620180458.5041-1-bijan311@gmail.com> <20250620202155.98021-1-sj@kernel.org> In-Reply-To: From: Bijan Tabatabai Date: Mon, 23 Jun 2025 18:21:20 -0500 X-Gm-Features: AX0GCFvhM9bDmIKNz3hzb_T7Ftkp2AGOE2ZRMfDXHquDjGFrrsP8UEg9t-r2yYQ Message-ID: Subject: Re: [RFC PATCH v2 0/2] mm/damon/paddr: Allow interleaving in migrate_{hot,cold} actions To: Gregory Price Cc: SeongJae Park , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, david@redhat.com, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com, bijantabatab@micron.com, venkataravis@micron.com, emirakhur@micron.com, ajayjoshi@micron.com, vtavarespetr@micron.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 67B55140006 X-Stat-Signature: ktm7xih8tf71nrq4koohpwwddefg1h6r X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1750720893-76610 X-HE-Meta: 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 hmMZ6PK8 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Gregory, On Mon, Jun 23, 2025 at 2:28=E2=80=AFPM Gregory Price w= rote: > > On Fri, Jun 20, 2025 at 01:21:55PM -0700, SeongJae Park wrote: > > Hi Bijan, > > > > On Fri, 20 Jun 2025 13:04:56 -0500 Bijan Tabatabai = wrote: > > > > [...] > > > This patch set adds the mechanism for dynamically changing how applic= ation > > > data is interleaved across nodes while leaving the policy of what the > > > interleave weights should be to userspace. It does this by modifying = the > > > migrate_{hot,cold} DAMOS actions to allow passing in a list of migrat= ion > > > targets to their target_nid parameter. When this is done, the > > > migrate_{hot,cold} actions will migrate pages between the specified n= odes > > > using the global interleave weights found at > > > /sys/kernel/mm/mempolicy/weighted_interleave/node. This functional= ity > > > can be used to dynamically adjust how pages are interleaved by changi= ng the > > > global weights. When only a single migration target is passed to > > > target_nid, the migrate_{hot,cold} actions will act the same as befor= e. > > > > This means users are required to manipulate two interfaces. DAMON sysf= s for > > target nodes, and weighted_interleave sysfs for weights. I don't think= this > > coupling is very ideal. > > > > Just tossing this out there - weighted interleave sysfs entries *should* > be automatic, and the preferred weights shouldn't really ever change > over time. Even if they did, if it's the result of devices coming and > going - the updates should also be automatic. I'm not convinced this is true. If you have a workload that can saturate the local bandwidth but not the remote bandwidth, wouldn't you want the interleave weights to be more biased towards local memory than you would for a workload that can saturate both the local and remote bandwidth? > So, in practice, a usually probably only has to twiddle DAMON. That being said, I don't mind the idea of the mempolicy weights being left untouched as a reasonable starting point for bandwidth intensive applications and leaving the fine tuning to DAMON. Thanks, Bijan