From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id BFB9A20B34 for ; Wed, 19 Jun 2024 09:32:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718789525; cv=none; b=P1nNBxa3FizuEslqIMQPrpqIYX2sku8DAOnWbYnPDmWes6iDgD+vkDZpA5kqlP3P/29M/zd5HYwxMOvpmDPTr78xN7Q17RfgVEZdyLvpn/bQIzxd9slXfdNtOHWc62TFvFlGt1dRn3MlcwEz/dSaisx9Z05I0q+0DlZuS+09SB4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718789525; c=relaxed/simple; bh=V1ffL/PhAeo4peyAcLvwR8276v37fCfBHyqqvQXiUew=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Yo3gwDpQJm8TY9oig5hO5IMoAV+JWLdRi7JktOhIQcDCWyS+72XCAsJ14L0Ygg6m0y+yrD6d1OBklIcD85D0JD4Ht2dxsteCEP2E9QPh4rL6PZCRMzkujbiKtPmK698ADnUVirXwS1DwaUxGEZm8HYnBax7AtPjyBVx8PKqsmfM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D2325DA7; Wed, 19 Jun 2024 02:32:26 -0700 (PDT) Received: from [10.1.36.163] (XHFQ2J9959.cambridge.arm.com [10.1.36.163]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 246B53F64C; Wed, 19 Jun 2024 02:32:01 -0700 (PDT) Message-ID: <1f02756f-a753-459b-8e8b-85fbbe5c5126@arm.com> Date: Wed, 19 Jun 2024 10:31:59 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 0/2] mm: swap: mTHP swap allocator base on swap cluster order Content-Language: en-GB To: Chris Li , Andrew Morton Cc: Kairui Song , "Huang, Ying" , Kalesh Singh , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Barry Song References: <20240619-swap-allocator-v3-0-e973a3102444@kernel.org> From: Ryan Roberts In-Reply-To: <20240619-swap-allocator-v3-0-e973a3102444@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 19/06/2024 10:20, Chris Li wrote: > This is the short term solutiolns "swap cluster order" listed > in my "Swap Abstraction" discussion slice 8 in the recent > LSF/MM conference. > > When commit 845982eb264bc "mm: swap: allow storage of all mTHP > orders" is introduced, it only allocates the mTHP swap entries > from new empty cluster list. It has a fragmentation issue > reported by Barry. > > https://lore.kernel.org/all/CAGsJ_4zAcJkuW016Cfi6wicRr8N9X+GJJhgMQdSMp+Ah+NSgNQ@mail.gmail.com/ > > The reason is that all the empty cluster has been exhausted while > there are planty of free swap entries to in the cluster that is > not 100% free. > > Remember the swap allocation order in the cluster. > Keep track of the per order non full cluster list for later allocation. > > User impact: For users that allocate and free mix order mTHP swapping, > It greatly improves the success rate of the mTHP swap allocation after the > initial phase. > > Barry provides a test program to show the effect: > https://lore.kernel.org/linux-mm/20240615084714.37499-1-21cnbao@gmail.com/ > > Without: > $ mthp-swapout > Iteration 1: swpout inc: 222, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 2: swpout inc: 219, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 3: swpout inc: 222, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 4: swpout inc: 219, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 5: swpout inc: 110, swpout fallback inc: 117, Fallback percentage: 51.54% > Iteration 6: swpout inc: 0, swpout fallback inc: 230, Fallback percentage: 100.00% > Iteration 7: swpout inc: 0, swpout fallback inc: 229, Fallback percentage: 100.00% > Iteration 8: swpout inc: 0, swpout fallback inc: 223, Fallback percentage: 100.00% > Iteration 9: swpout inc: 0, swpout fallback inc: 224, Fallback percentage: 100.00% > Iteration 10: swpout inc: 0, swpout fallback inc: 216, Fallback percentage: 100.00% > Iteration 11: swpout inc: 0, swpout fallback inc: 212, Fallback percentage: 100.00% > Iteration 12: swpout inc: 0, swpout fallback inc: 224, Fallback percentage: 100.00% > Iteration 13: swpout inc: 0, swpout fallback inc: 214, Fallback percentage: 100.00% > > $ mthp-swapout -s > Iteration 1: swpout inc: 222, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 2: swpout inc: 227, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 3: swpout inc: 222, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 4: swpout inc: 224, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 5: swpout inc: 33, swpout fallback inc: 197, Fallback percentage: 85.65% > Iteration 6: swpout inc: 0, swpout fallback inc: 229, Fallback percentage: 100.00% > Iteration 7: swpout inc: 0, swpout fallback inc: 223, Fallback percentage: 100.00% > Iteration 8: swpout inc: 0, swpout fallback inc: 219, Fallback percentage: 100.00% > Iteration 9: swpout inc: 0, swpout fallback inc: 212, Fallback percentage: 100.00% > > With: > $ mthp-swapout > Iteration 1: swpout inc: 222, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 2: swpout inc: 219, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 3: swpout inc: 222, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 4: swpout inc: 219, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 5: swpout inc: 227, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 6: swpout inc: 230, swpout fallback inc: 0, Fallback percentage: 0.00% > ... > Iteration 94: swpout inc: 224, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 95: swpout inc: 221, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 96: swpout inc: 229, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 97: swpout inc: 219, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 98: swpout inc: 222, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 99: swpout inc: 223, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 100: swpout inc: 224, swpout fallback inc: 0, Fallback percentage: 0.00% > > $ mthp-swapout -s > Iteration 1: swpout inc: 222, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 2: swpout inc: 227, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 3: swpout inc: 222, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 4: swpout inc: 224, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 5: swpout inc: 230, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 6: swpout inc: 229, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 7: swpout inc: 223, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 8: swpout inc: 219, swpout fallback inc: 0, Fallback percentage: 0.00% > ... > Iteration 94: swpout inc: 223, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 95: swpout inc: 212, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 96: swpout inc: 220, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 97: swpout inc: 220, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 98: swpout inc: 216, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 99: swpout inc: 223, swpout fallback inc: 0, Fallback percentage: 0.00% > Iteration 100: swpout inc: 225, swpout fallback inc: 0, Fallback percentage: 0.00% Excellent! > > Reported-by: Barry Song <21cnbao@gmail.com> > Signed-off-by: Chris Li > --- > Changes in v3: > - Using V1 as base. > - Rename "next" to "list" for the list field, suggested by Ying. > - Update comment for the locking rules for cluster fields and list, > suggested by Ying. > - Allocate from the nonfull list before attempting free list, suggested > by Kairui. Sorry I didn't follow this original conversation. But the original intent of having a per-cpu current cluster was to prevent interleving pages from multiple processes and therefore optimize IO. See commit ebc2a1a69111 ("swap: make cluster allocation per-cpu"). I wonder if this change could lead to a swap performance regression in the common order-0 case? Thanks, Ryan > - Link to v2: https://lore.kernel.org/r/20240614-swap-allocator-v2-0-2a513b4a7f2f@kernel.org > > Changes in v2: > - Abandoned. > - Link to v1: https://lore.kernel.org/r/20240524-swap-allocator-v1-0-47861b423b26@kernel.org > > --- > Chris Li (2): > mm: swap: swap cluster switch to double link list > mm: swap: mTHP allocate swap entries from nonfull list > > include/linux/swap.h | 30 +++---- > mm/swapfile.c | 248 +++++++++++++++++---------------------------------- > 2 files changed, 95 insertions(+), 183 deletions(-) > --- > base-commit: 19b8422c5bd56fb5e7085995801c6543a98bda1f > change-id: 20240523-swap-allocator-1534c480ece4 > > Best regards,