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Fri, 07 Aug 2026 09:18:32 -0700 (PDT) From: Liew Rui Yan To: sj@kernel.org Cc: aethernet65535@gmail.com, damon@lists.linux.dev, linux-mm@kvack.org Subject: Re: [PATCH 2/2] mm/damon: skip deactivated schemes in watermark checks and add fallback sleep Date: Sat, 8 Aug 2026 00:18:40 +0800 Message-ID: <20260807161840.56993-1-aethernet65535@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260807140739.91238-1-sj@kernel.org> References: <20260807140739.91238-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: mt66uoqpj4k5ns939hj9y71sk8hrccfz X-Rspamd-Queue-Id: 1A7812000B X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1786119513-236740 X-HE-Meta: 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 TpUt7qQn FNcuq8M9a8idLjarE/3S7ilo3YX+mcVmpVigtiHwW9rZmMDR1YxzaUfKCjdnUUYOVR1UDxRd0YortDKHFxm3/fWyYkJZllDxt1RN/vZ/Oe7wyaN894Q0GNX3UFUFySVm2LBns4iyxu5nkpdGDs1L2jm3qZuYvh7MEabDxUVOGp3eastCyXDqPj2aj3G8IeEhr6QSr4cLk7kM34jsRjI/vRgB7M70BEX+z+IXvyjSDzAS9hI3KZMKwjcxJ6GtKKhCELGyrBl5hbK5ObVZNgrLz1bInfsRDI00MGOO5ZiyWs7YSJWGF32oVF0dJ+BGuYJemGyxu9cuVJZfuKgEV6JztacRHn6moLFei//Sp3AvwDtoV/eMgh73SI8R33Y17oBDrQPUjMli+1wcKzj2kkYCGjyLSSilRFFraEE0+Gc3rmj3awKU0bgNq/aJvzqagYv7MOU2zK2m8mD9+4b4= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi SJ, On Fri, 7 Aug 2026 07:07:39 -0700 SJ Park wrote: > This is an intended implementation. > > When all schemes are deactivated by watermarks, DAMON stops monitoring. It was > implemented in the way because we didn't want DAMON consumes system resource in > the case. But, later it turned out DAMON's resource consumption is really > negligible. Rather, it is turned out that it makes DAMON runs with stale > history when it is activated again. Particularly, regions have 'age' and their > start/end addresses that was emerged before the deactivation. Those are > meaningless and could even cause wrong DAMOS decisions. > > We don't want that anymore. For a case the user really want DAMON completely > stops, we introduced 'pause'. For max_nr_snapshot-based deactivation, we don't > intend to completely stop DAMON. > > Maybe the documentation can be updated to further clarify this. Thank you for your detailed explanation! I also glad to hear that DAMON's monitoring's resource consumption is negligible, since I plan to add a contexts//always_monitoring parameter later on, allowing users to decide for themselves whether to keep monitoring even all schemes is deactivated by watermarks. Best regards, Rui Yan