From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from invmail4.hynix.com (exvmail4.hynix.com [166.125.252.92]) by smtp.subspace.kernel.org (Postfix) with ESMTP id CD2201411F9 for ; Tue, 4 Jun 2024 08:45:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=166.125.252.92 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717490748; cv=none; b=uf751IFQEqNrd4pULg5DI2Y6Tn4ew57R1UzFHX2zLjYRj2AAyJkhER78MySLu7PoknEWuQvLkvcfwC/WYrzdNye2Uzd1i7DM0mGyIQv3t0/JTTg0WTcWccrPPlQYUDZhDcRRXNwsN/N7sAARkGcE/gh+ARL6aoRNSrGP6LRPuB0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717490748; c=relaxed/simple; bh=OQIffwSMMzPTLMkbkLwlXwwOwo3Bx6H8Zm5F5P0mvfI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=j7Zt8jm1r4dllnBhqvJVoIwV8bGEs6x3hYG9E/ZHU0HwPclfb5HsTAxG/DXtCXlIbIaDoTPMUqSJn25/DFCKHZueI6rGWgO8m5RZ9JYyIHcmCfXzQJmZln2J0JE+nxNOjV33OF3Uy5NcHoSgYdRddrc00jFCZCWOiMBpyWjRXRU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sk.com; spf=pass smtp.mailfrom=sk.com; arc=none smtp.client-ip=166.125.252.92 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sk.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sk.com X-AuditID: a67dfc5b-d85ff70000001748-9a-665ed43276cc Date: Tue, 4 Jun 2024 17:45:33 +0900 From: Byungchul Park To: "Huang, Ying" Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com, hannes@cmpxchg.org, iamjoonsoo.kim@lge.com, rientjes@google.com Subject: Re: [PATCH v2] mm: let kswapd work again for node that used to be hopeless but may not now Message-ID: <20240604084533.GA68919@system.software.com> References: <20240604072323.10886-1-byungchul@sk.com> <87bk4hcf7h.fsf@yhuang6-desk2.ccr.corp.intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87bk4hcf7h.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrNLMWRmVeSWpSXmKPExsXC9ZZnoa7Rlbg0g/ZzOhZz1q9hs1i9yddi ZXczm8XlXXPYLO6t+c9q0bZkI5PFyVmTWRzYPQ6/ec/ssWBTqcfiPS+ZPDZ9msTu0fX2CpPH iRm/WTw+b5ILYI/isklJzcksSy3St0vgytixSr/gq0TF/kV3mRsYzwt3MXJySAiYSGzffIKt i5EDzF7RYAQSZhFQkVh05CoriM0moC5x48ZPZhBbREBD4tPC5exdjFwczAJrGSWOXG1hBekV FkiVOL49AKSGV8BC4t2xj2wgtpBApsSDnXuZIeKCEidnPmEBsZkFtCRu/HvJBNLKLCAtsfwf B4jJKWAnseOqFUiFqICyxIFtx5lANkkI7GGTaN01jR3iYkmJgytusExgFJiFZOosJFNnIUxd wMi8ilEoM68sNzEzx0QvozIvs0IvOT93EyMwyJfV/onewfjpQvAhRgEORiUeXoNFsWlCrIll xZW5hxglOJiVRHj76qLThHhTEiurUovy44tKc1KLDzFKc7AoifMafStPERJITyxJzU5NLUgt gskycXBKNTDapPX/Ngqcc/vqn09y+ic049a/9NJIvN9i8iL3+B1T7Tls9ZN+BTTJbJ2gxT/f qt1ueU55CnOnzOa1s1OOrvux9IVT8uZXijGp0/obnKPPPu6u/b5PgIcx5a+hvNL3o+u3L+1U 4zii9PIZ40bDJyG9hwvlNlcem/Bdee7NxZ+6+aSdW8/UP1uuxFKckWioxVxUnAgAsAtk0m4C AAA= X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFjrELMWRmVeSWpSXmKPExsXC5WfdrGt0JS7NoPuPqMWc9WvYLFZv8rVY 2d3MZnF47klWi8u75rBZ3Fvzn9WibclGJouTsyazOHB4HH7zntljwaZSj8V7XjJ5bPo0id2j 6+0VJo8TM36zeCx+8YHJ4/MmuQCOKC6blNSczLLUIn27BK6MHav0C75KVOxfdJe5gfG8cBcj B4eEgInEigajLkZODhYBFYlFR66ygthsAuoSN278ZAaxRQQ0JD4tXM7excjFwSywllHiyNUW VpBeYYFUiePbA0BqeAUsJN4d+8gGYgsJZEo82LmXGSIuKHFy5hMWEJtZQEvixr+XTCCtzALS Esv/cYCYnAJ2EjuuWoFUiAooSxzYdpxpAiPvLCTNs5A0z0JoXsDIvIpRJDOvLDcxM8dUrzg7 ozIvs0IvOT93EyMwZJfV/pm4g/HLZfdDjAIcjEo8vBYrY9OEWBPLiitzDzFKcDArifD21UWn CfGmJFZWpRblxxeV5qQWH2KU5mBREuf1Ck9NEBJITyxJzU5NLUgtgskycXBKNTD2vS5dvWlx DFtc/h/Xr4v1nzjOXPM39h8bk8le7bcT24+sSJhaemtfkve3wF9u77dUFlzo8X/xJ+bfzIse j39tbWc8nPb39eaw+/HHF0+3PhHZ5LGy8uyiig5mX4dG95/VHtImYU13fh1I8/5ov/SBWtDt BEalJ29Z0iOWL9rEEff2zJpb05ZMVmIpzkg01GIuKk4EAL/tOjJVAgAA X-CFilter-Loop: Reflected On Tue, Jun 04, 2024 at 03:57:54PM +0800, Huang, Ying wrote: > Byungchul Park writes: > > > Changes from v1: > > 1. Don't allow to resume kswapd if the system is under memory > > pressure that might affect direct reclaim by any chance, like > > if NR_FREE_PAGES is less than (low wmark + min wmark)/2. > > > > --->8--- > > From 6c73fc16b75907f5da9e6b33aff86bf7d7c9dd64 Mon Sep 17 00:00:00 2001 > > From: Byungchul Park > > Date: Tue, 4 Jun 2024 15:27:56 +0900 > > Subject: [PATCH v2] mm: let kswapd work again for node that used to be hopeless but may not now > > > > A system should run with kswapd running in background when under memory > > pressure, such as when the available memory level is below the low water > > mark and there are reclaimable folios. > > > > However, the current code let the system run with kswapd stopped if > > kswapd has been stopped due to more than MAX_RECLAIM_RETRIES failures > > until direct reclaim will do for that, even if there are reclaimable > > folios that can be reclaimed by kswapd. This case was observed in the > > following scenario: > > > > CONFIG_NUMA_BALANCING enabled > > sysctl_numa_balancing_mode set to NUMA_BALANCING_MEMORY_TIERING > > numa node0 (500GB local DRAM, 128 CPUs) > > numa node1 (100GB CXL memory, no CPUs) > > swap off > > > > 1) Run a workload with big anon pages e.g. mmap(200GB). > > 2) Continue adding the same workload to the system. > > 3) The anon pages are placed in node0 by promotion/demotion. > > 4) kswapd0 stops because of the unreclaimable anon pages in node0. > > 5) Kill the memory hoggers to restore the system. > > > > After restoring the system at 5), the system starts to run without > > kswapd. Even worse, tiering mechanism is no longer able to work since > > the mechanism relies on kswapd for demotion. > > We have run into the situation that kswapd is kept in failure state for > long in a multiple tiers system. I think that your solution is too My solution just gives a chance for kswapd to work again even if kswapd_failures >= MAX_RECLAIM_RETRIES, if there are potential reclaimable folios. That's it. > limited, because OOM killing may not happen, while the access pattern of I don't get this. OOM will happen as is, through direct reclaim. > the workloads may change. We have a preliminary and simple solution for > this as follows, > > https://git.kernel.org/pub/scm/linux/kernel/git/vishal/tiering.git/commit/?h=tiering-0.8&id=17a24a354e12d4d4675d78481b358f668d5a6866 Whether tiering is involved or not, the same problem can arise if kswapd gets stopped due to kswapd_failures >= MAX_RECLAIM_RETRIES. Byungchul > where we will try to wake up kswapd to check every 10 seconds if kswapd > is in failure state. This is another possible solution. > > > However, the node0 has pages newly allocated after 5), that might or > > might not be reclaimable. Since those are potentially reclaimable, it's > > worth hopefully trying reclaim by allowing kswapd to work again. > > > > [snip] > > -- > Best Regards, > Huang, Ying