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Mon, 23 Jun 2025 12:28:39 -0700 (PDT) Received: from gourry-fedora-PF4VCD3F ([2620:10d:c091:400::5:e19e]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6fd094330fcsm48301596d6.31.2025.06.23.12.28.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Jun 2025 12:28:39 -0700 (PDT) Date: Mon, 23 Jun 2025 14:28:37 -0500 From: Gregory Price To: SeongJae Park Cc: Bijan Tabatabai , 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 Subject: Re: [RFC PATCH v2 0/2] mm/damon/paddr: Allow interleaving in migrate_{hot,cold} actions Message-ID: References: <20250620180458.5041-1-bijan311@gmail.com> <20250620202155.98021-1-sj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250620202155.98021-1-sj@kernel.org> X-Rspamd-Server: rspam11 X-Rspam-User: X-Rspamd-Queue-Id: DCE0314000A X-Stat-Signature: yd97eotxzu5xd4bqpyh4zxi5tw8jdsqw X-HE-Tag: 1750706920-555438 X-HE-Meta: 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 zJ4z8kb8 fozhI4IGXbrpF2qKOFMuRwa81am9PtTcx0Cxuttau+VAauJCN6ubKErMJVRLMrV61MGkxm0F/yvNqD4P9KMbv2TU2MSXmvBfauLUlT6qeyjpuWnhu438Uib5yoLpLgXp14ydKEjfv8u3Dn9LziepvM+OjLmczBrxoA0H+Y+MYk4LPatRoHkeoqb2sh0fjVGIJcNuo52V9PC9x5iiK5ee6Efn6Psisoy0gGQw303Ck9JdFiOarhtWIa0hBWFy1II9LPBU9G6iDTsVJXlMu9V7ih1eMmREqgF2BUHxw8QBpdr0cjG2lXLWfpGrvNFXgdVEuUochpt1R84DmtDqFI5LSJoA5+2ygVjY1rnvkLLsfwCwpC6zj/8uO/XG/9oe0MACFSBbpnUWtyuL77zYi8h9XRuAzSqyaKKkwieZPrC2JiCQV6HgV2DXJMoLONhn3A1mmWngmj8pT0fMp3/vWPzjSSzO9lcOCPhJJd2ibNkiVLhUpuBWQMe6Qq9yLXRCdgc1AJh6q 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: 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 application > > 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 migration > > targets to their target_nid parameter. When this is done, the > > migrate_{hot,cold} actions will migrate pages between the specified nodes > > using the global interleave weights found at > > /sys/kernel/mm/mempolicy/weighted_interleave/node. This functionality > > can be used to dynamically adjust how pages are interleaved by changing the > > global weights. When only a single migration target is passed to > > target_nid, the migrate_{hot,cold} actions will act the same as before. > > This means users are required to manipulate two interfaces. DAMON sysfs 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. So, in practice, a usually probably only has to twiddle DAMON. I don't have a strong opinion on whether DAMON should leverage the mempolicy interface, but I think the way it is designed now is acceptable. ~Gregory