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Fri, 1 May 2026 06:28:11 +0000 Date: Thu, 30 Apr 2026 23:28:08 -0700 From: Matthew Brost To: Andrew Morton CC: , , "Dave Chinner" , Qi Zheng , "Roman Gushchin" , Johannes Weiner , Shakeel Butt , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Tvrtko Ursulin , Thomas =?iso-8859-1?Q?Hellstr=F6m?= , Carlos Santa , Christian Koenig , Huang Rui , Matthew Auld , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Daniel Colascione , "David Hildenbrand" , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , "Mike Rapoport" , Suren Baghdasaryan , "Michal Hocko" , , Subject: Re: [PATCH v4 0/6] mm, drm/ttm, drm/xe: Avoid reclaim/eviction loops under fragmentation Message-ID: References: <20260430191809.2142544-1-matthew.brost@intel.com> <20260430160105.a3b74ec3bb316bbfbf8f9808@linux-foundation.org> Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260430160105.a3b74ec3bb316bbfbf8f9808@linux-foundation.org> X-ClientProxiedBy: SJ2PR07CA0015.namprd07.prod.outlook.com (2603:10b6:a03:505::28) To PH7PR11MB6522.namprd11.prod.outlook.com (2603:10b6:510:212::12) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH7PR11MB6522:EE_|MW4PR11MB6887:EE_ X-MS-Office365-Filtering-Correlation-Id: 629a5b77-bee2-4af0-618c-08dea74ad161 X-MS-Exchange-SenderADCheck: 1 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X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: m6lWkzdsWLr+T8VjFBZFFS5vsslbmwKxDrE2GcgabKbOt32ZzpkH1r9svDwEVeBkwFUWJFqE+47yL4Xq4UvGSA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR11MB6887 X-OriginatorOrg: intel.com On Thu, Apr 30, 2026 at 04:01:05PM -0700, Andrew Morton wrote: > On Thu, 30 Apr 2026 12:18:03 -0700 Matthew Brost wrote: > > > TTM allocations at higher orders can drive Xe into a pathological > > reclaim loop when memory is fragmented: > > > > kswapd → shrinker → eviction → rebind (exec ioctl) → repeat > > > > In this state, reclaim is triggered despite substantial free memory, > > but fails to produce contiguous higher-order pages. The Xe shrinker then > > evicts active buffer objects, increasing faulting and rebind activity > > and further feeding the loop. The result is high CPU overhead and poor > > GPU forward progress. > > > > ... > > > > This series addresses the issue in two ways: > > > > TTM: Restrict direct reclaim to beneficial_order. Larger allocations > > use __GFP_NORETRY to fail quickly rather than triggering reclaim. > > > > Xe: Introduce a heuristic in the shrinker to avoid eviction when > > running under kswapd and the system appears memory-rich but > > fragmented. > > Please cc everyone on all the patches? It's kind of annoying to have > to hunt around to find out how these proposed changes will be used. > Personal preference, anyway. > Will do - we discussed this in the past and thought we landed on Cc everyone on the cover then individual patches but will blast everyone going forward. > AI review flagged a few possible issues: > https://sashiko.dev/#/patchset/20260430191809.2142544-1-matthew.brost@intel.com Idk, who authors sashiko but what make it really nice if you could reply to it to talk things out. Looking at replies... - 'Could this global counter drift significantly' this is looks right for multi-CPU which isn't really the target here, but will adjust - 'Additionally, does NR_FREE_PAGES implicitly include CMA pages?' this is looks right, will adjust - 'Can high_wmark_pages(zone) evaluate to zero during early boot' theoretically possible (?), but non-issue IMO, certainly a GPU shrinker which is current use case this is impossible but maybe add a warn_on if high_wmark_pages(zone) returns zero - 'Is this description accurate?' I inverted the TTM kernel doc vs the code, will fix Matt