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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , , Subject: Re: [PATCH v2 1/5] mm: Introduce zone_appears_fragmented() Message-ID: References: <20260423055656.1696379-1-matthew.brost@intel.com> <20260423055656.1696379-2-matthew.brost@intel.com> Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-ClientProxiedBy: BY5PR03CA0009.namprd03.prod.outlook.com (2603:10b6:a03:1e0::19) To PH7PR11MB6522.namprd11.prod.outlook.com (2603:10b6:510:212::12) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH7PR11MB6522:EE_|DM3PPF1721FD39C:EE_ X-MS-Office365-Filtering-Correlation-Id: 396f8743-2f61-432b-703c-08dea1016982 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; ARA:13230040|1800799024|366016|376014|7416014|18002099003|22082099003|56012099003; X-Microsoft-Antispam-Message-Info: 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=?utf-8?B?RXZBL2FBQlRpa0szd3hxWjA3bjFpMGM0aU5NZ2ZoT1RqSHN5TnBxUT09?= X-Exchange-RoutingPolicyChecked: Zz78Q8yucoHhBuOLd5bpbiWy+tf8DCu/16vMwDnG63GWseqlNGUZK51BhSSW5RTFcwLSznDlxuyK8SgflEv6TKJ/HqMVKTcc8f75fVchqGx28t/zYBClIQ7n0McjHN6Va9DOxX3cVYjCeFqHONFywSpLEs5nviuXB7qzMwFwjJ4MhYJRYFNEb3N03xckGPxkPiLb15l2rnHjxTHI6YGIEfabGS0fT6KirNj4ZJz5JwwpzQVyL+OC+RtStmJB+Bq53bO1ZlvfUWGpwGvdlAZs9X6GBLMD6CDIgtkSnHuGJQgTiDrtlf6Hw/iG/1+80NkeKtg9fdFJp8Y2JKzWMPyV+Q== X-MS-Exchange-CrossTenant-Network-Message-Id: 396f8743-2f61-432b-703c-08dea1016982 X-MS-Exchange-CrossTenant-AuthSource: PH7PR11MB6522.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Apr 2026 06:27:37.1472 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: EjLjLRx84OxeTOYQHz9RMUVHFM0Zv/4ek3wWlWtreywZe5wPRZ1pOvMGkDMEs2X+GJAr19fYYwEpd/ta+SRREQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM3PPF1721FD39C X-OriginatorOrg: intel.com X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" On Wed, Apr 22, 2026 at 11:16:37PM -0700, Matthew Brost wrote: > On Thu, Apr 23, 2026 at 04:04:32PM +1000, Balbir Singh wrote: > > On 4/23/26 15:56, Matthew Brost wrote: > > > Introduce zone_appears_fragmented() as a lightweight helper to allow > > > subsystems to make coarse decisions about reclaim behavior in the > > > presence of likely fragmentation. > > > > > > The helper implements a simple heuristic: if the number of free pages > > > in a zone exceeds twice the high watermark, the zone is considered to > > > have ample free memory and allocation failures are more likely due to > > > fragmentation than overall memory pressure. > > > > > > This is intentionally imprecise and is not meant to replace the core > > > MM compaction or fragmentation accounting logic. Instead, it provides > > > a cheap signal for callers (e.g., shrinkers) that wish to avoid > > > overly aggressive reclaim when sufficient free memory exists but > > > high-order allocations may still fail. > > > > > > No functional changes; this is a preparatory helper for future users. > > > > > > Cc: Thomas Hellström > > > Cc: Andrew Morton > > > Cc: David Hildenbrand > > > Cc: Lorenzo Stoakes > > > Cc: "Liam R. Howlett" > > > Cc: Vlastimil Babka > > > Cc: Mike Rapoport > > > Cc: Suren Baghdasaryan > > > Cc: Michal Hocko > > > Cc: linux-mm@kvack.org > > > Cc: linux-kernel@vger.kernel.org > > > Signed-off-by: Matthew Brost > > > --- > > > include/linux/vmstat.h | 13 +++++++++++++ > > > 1 file changed, 13 insertions(+) > > > > > > diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h > > > index 3c9c266cf782..568d9f4f1a1f 100644 > > > --- a/include/linux/vmstat.h > > > +++ b/include/linux/vmstat.h > > > @@ -483,6 +483,19 @@ static inline const char *zone_stat_name(enum zone_stat_item item) > > > return vmstat_text[item]; > > > } > > > > > > +static inline bool zone_appears_fragmented(struct zone *zone) > > > +{ > > > + /* > > > + * Simple heuristic: if the number of free pages is more than twice the > > > + * high watermark, this strongly suggests that the zone is heavily > > > + * fragmented when called from a shrinker. > > > + */ > > > + if (zone_page_state(zone, NR_FREE_PAGES) > high_wmark_pages(zone) * 2) > > > + return true; > > > + > > > + return false; > > > +} > > > + > > > #ifdef CONFIG_NUMA > > > static inline const char *numa_stat_name(enum numa_stat_item item) > > > { > > > > > > Without any usage/users, this is hard to review. I don't understand the heuristic > > or it's logic as applied to fragmentation either. > > > > Sorry—it’s always confusing who to CC on cross-subsystem series. Last > time this occurred, we agreed to CC everyone listed in the cover letter, > which I did. Anyway, let me provide the Patchwork links... > > Cover letter: https://patchwork.freedesktop.org/series/165329/ > TTM patch which uses this: https://patchwork.freedesktop.org/patch/720036/?series=165329&rev=1 > Xe side which uses the TTM helper: https://patchwork.freedesktop.org/patch/720031/?series=165329&rev=1 > Also if you want grab whole series locally here is what I do when I'm missed on a Cc: b4 mbox mutt -f So here, with msg-id from cover letter: b4 mbox 20260423055656.1696379-1-matthew.brost@intel.com mutt -f ./20260423055656.1696379-1-matthew.brost@intel.com.mbx Matt > Matt > > > Balbir