From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 576551397 for ; Sat, 8 Aug 2026 00:07:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786147667; cv=none; b=c6gUPuAtGSqGiqm4Uqj3WKLTmqyQ09yFxH4yw+xzUbmlmE2EpnEjieE+e6U3/FOzghEm95bImuWtF05pqZd5jlX2kiBAlMv1F/xO8FJiTQZp/2OopbL/SyxreDXcdyVpNnP0tvoFg55a5UeORxmq30eUWLbwySeeilrVGrZcpbA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786147667; c=relaxed/simple; bh=ibGMZwYwCjHCpha6ArnzxNaXxnR5zNAiI9eY8j4uHSw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=s6jqiqll+PF+JXuIX6kfKizTS6wsX2pEkHlFHaSebA2Th8HJQ4HBG5ihJcopp4oVYd1x1vCGTn+65jPL4q83bmvhLaUpicksjL+Yb+xt8p/SIVH4zAXhXb3+pp6eZZwvTAXpzQfGgzoNmthn5JBTEtYWh6HNVqVIh6myx0ZvgUs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ZoFR3W53; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ZoFR3W53" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DA3EC1F000E9; Sat, 8 Aug 2026 00:07:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786147666; bh=jURskxvxN8Et2Wft8lg3avApYLlxcoCblCUkQrEksBE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ZoFR3W535iIJL7/T3VlGOvG4vWl1jyomma/oC/XHtmSdwpFzeG8s6nNVD3/3WBcWU 9TTIXF0owhgDtfiVGEd19jH3fF5ghW1lTOj2doZh7Up6zVGP8R9sBvX4y4GvRP3cPC TIUvmqUmf30++8P8yZIda5tD4IzmwzUpipQ5sh3aYB73bGFvmlCfxKdr6gLPMbRY3e Wo50B0fql//H0hbOUv86hcq1vpOVtfHnA7/EJPqatDy2zm3tHikTi+KbnVpkmlqmUy t8qft6XxZuxRcj8tHsm3/aKsQKRiW7LgLediOtap3G3plM6iWzBWgxvyj0PZR1xWD7 OKXE0Gr7+JGVA== From: SJ Park To: Liew Rui Yan Cc: SJ Park , 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: Fri, 7 Aug 2026 17:07:38 -0700 Message-ID: <20260808000739.1308-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260807161840.56993-1-aethernet65535@gmail.com> References: Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Sat, 8 Aug 2026 00:18:40 +0800 Liew Rui Yan wrote: > 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. Unless it is for your real use case, I'd not encourage improving watermarks. Here are contexts. Watermarks was initially developed for DAMON_RECLAIM. But I found it is difficult to be extended for other use cases. Also it has the aobve mentioned problem: losing the monitoring results that was converged over time. I'm planning to develop an alternative superior feature and deprecate watermarks over time. The plan is not having a high priority because I don't show real requirement of that. If anyone wants it for their real use case, please let me know so that I can prioritize. Thanks, SJ [...]