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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?q9OQug6Dgy9nuyTQBsMgDvkJv6iej2ITWUNcQUKKb/OWyfbAu2diuOg95/Ee?= =?us-ascii?Q?tEElMRprKQs4MdDtlCOjIySyNEMK8w/ANz4bmv24FosFVuutgqZehZWii6TR?= =?us-ascii?Q?eNH2fCjdLpyqWF6K8wYaUdhoY3sZqbdbvQYZFmdTfapP3CzXsl0oarNWyV2o?= =?us-ascii?Q?pS1l8e2g/kT2vIDlmKkkyh1Xb5b819lWhgWJaJawpIcOlPUQgd3W1/GVqRhX?= =?us-ascii?Q?8CbGN3d0vTr31j3MTpZ7OvkniaKxBMAwwAxDmusD5g50HNUThYTpsR8dMotd?= =?us-ascii?Q?QyX0mcClbdQbcv9pCBal6oM8HAFvn09WsdQ//VH+0dGksQv/sucoZbXI/xEt?= =?us-ascii?Q?o0zjb6X5XI4oB5HtCLkyzHsIDAhg/jGOlwNDTLBHQevgQ+UyJbLwMKtVueLm?= =?us-ascii?Q?mHx/+zupofgGc2k1D0eHTMDrhfvGUBnp8+HODsdQ19HAuOZ/tFkyAfB01gAK?= =?us-ascii?Q?L4mkHOAuiUZY7TiTkrNSxW0ewIeyNXZp9xKV6dAx5eVXIjeViCzTwi0OWqpT?= =?us-ascii?Q?dr9KNrFuD7MrM5menzElBw/L344/7y/kVP6SUS8RHzeJD7L0TOQkgcdWRd2/?= =?us-ascii?Q?PWPwwBgf1WlaUGBt43ozJSKHmerV7rdT/dOjluXJuhkzEwJDHEX/FOcWstAu?= =?us-ascii?Q?pUfxpCnbG88qaxo/CMH6mUQf0/cd13wEqZxPrMDmnLzGYiTIfU0sHqymZWKm?= =?us-ascii?Q?gvz6s8Q07XsSFZS3ekS+9sXmutwZ5eWZNVskFpA/nJWXpet7pKsnIG/HulvQ?= =?us-ascii?Q?6eQ4PfKZIUY1+cOFSwiw8V0BI5Sc3K55iMZ5Ss9gH4vu7j0f8Dw0O8M0bj+0?= =?us-ascii?Q?JayP959hmnqC7R9DkqenrQD3DXPWRru0OlNaM8v6/eQ+313LDC3iQZX0BDr/?= =?us-ascii?Q?XpD0d6G+6N/2oCyYOvfHr5iCCfXNf9YI4icqquKIvC3H/3c7Mm8r2VDqi+Rf?= =?us-ascii?Q?pWThNpueave57ASQld8XMd9xU9/aTBGGLTk4mn2J5k2UXVYg/aHoDsipXDkd?= =?us-ascii?Q?Ub1MEuaAJeVSZWmEq1sYia3wHkglzBLCheErvwgaxlI4DQ4UOQ2lJMYJl1ak?= =?us-ascii?Q?zMDrL+U9D1rnR/0nfpBi3FC/60AQdEuGZm9gaaUgh+IKPCs7oeWNiMCii2kR?= =?us-ascii?Q?LfKST89eKVIK/SKbbE1zR6QML1zjYA4Zb6svWWsiUXhBZOW4JtIX0n2fIR3/?= =?us-ascii?Q?KXDobvzzE5mghC1P95hmSdLAEcLXw8vsx+dBB9702RVG5nflu8fGKrJMt6+O?= =?us-ascii?Q?42BnxXUyVpm1CfYn+tVIqQq5O6S76LiD+pnXn6//FEEZ8OzCH9sjuFfNzVFb?= =?us-ascii?Q?JMuPoM+aiyqfpjmw2sRNAWsgdT4/54hwSTaT6Z9X8BT5K2aWlqG4lycfO5ZV?= =?us-ascii?Q?8gc2sFWnpm8ufLI2xkfbNpYXKxWuZ1lXWlrXsYbOsi/0Vm39aGno1fsOHS1q?= =?us-ascii?Q?okQZBJ3cJqlxoSV3tNMBUpsxYKvFuqPgeMYfyAZL7IctnwPu9S32OnaHgwal?= =?us-ascii?Q?IHf9ovCMTVKLa/8j+UEYcsJFDgFREeyyEMb/m3hJKWrxB0v1DeTNfxZe+PIu?= =?us-ascii?Q?ED3MNJsYU5OFa5V9pQLpcBsS6uK0sqqmjus22MYP2H6GNJHvvbrA4eyC16WK?= =?us-ascii?Q?7zLy+FKcMymON++jRheerNiVV/57GXwSf7RKbd08cY9xER6nUTglwFh5CDh4?= =?us-ascii?Q?Uyexk+etDZBJMLPmj+c7puAdW4fjJ813HdPKXfTmGWihA3e4HNdou4YlymgE?= =?us-ascii?Q?HsYc4+3yzw=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: bfb046af-e644-44cd-304e-08ded7010bf9 X-MS-Exchange-CrossTenant-AuthSource: CH2PR12MB5001.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Jun 2026 23:41:05.0336 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: SFBQlLQSuZ8R9TNmsv7LYax5PqM+CRAF/XHpHT2vsmyVdnLTDICaG2ezbHYK/Aj7iPkG0bd+nuwQgHrN++wk8Q== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR12MB7068 On Mon, Jun 29, 2026 at 12:33:37PM -0400, Johannes Weiner wrote: > Neha reports that mapped shmem aren't considered for NUMA balancing, > noting convergence problems and bandwidth bottlenecking for cachelib > based workloads on tiered memory systems. > > Looking at the code and going through the git history, this doesn't > actually seem intentional: > > Commit fc3147245d19 ("mm: numa: Limit NUMA scanning to migrate-on-fault > VMAs") added a vma_policy_mof() gate to task_numa_work() so VMAs whose > policy lacks MPOL_F_MOF are skipped from NUMA balancing scans. The > motivation was a real usecase: Oracle was pinning shared segments with > mbind(MPOL_BIND) so trapping faults was both expensive and pointless. > > The handling of NULL from vm_ops->get_policy, however, treated "user > explicitly opted out" the same as "user never specified anything." For > VMAs whose shared policy is absent - the common case for shmem - the > scan was disabled too. > > This issue is old. It probably hurts less in conventional NUMA. But it's > very noticable on tiered systems, where entire tmpfs workingsets can get > stuck on lower-bandwidth memory. > > Fix this by having vma_policy_mof() use __get_vma_policy() directly, and > thereby handle the fallback to task policy (-> preferred_node_policy() > has MPOL_F_MOF per default). Every other consumer of vm_ops->get_policy > already handles it this way, the scan-eligibility check was the outlier. > > This preserves Mel's intended fix: don't scan stuff the user explicitly > pinned. But allow default policy vmas to participate in balancing. > > Reported-by: Neha Gholkar > Tested-by: Neha Gholkar > Fixes: fc3147245d19 ("mm: numa: Limit NUMA scanning to migrate-on-fault VMAs") > Signed-off-by: Johannes Weiner > --- > mm/mempolicy.c | 21 ++++++--------------- > 1 file changed, 6 insertions(+), 15 deletions(-) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index 36699fabd3c2..bba65898aee1 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -2057,24 +2057,15 @@ struct mempolicy *get_vma_policy(struct vm_area_struct *vma, > bool vma_policy_mof(struct vm_area_struct *vma) > { > struct mempolicy *pol; > + pgoff_t ilx; > + bool mof; > > - if (vma->vm_ops && vma->vm_ops->get_policy) { > - bool ret = false; > - pgoff_t ilx; /* ignored here */ > - > - pol = vma->vm_ops->get_policy(vma, vma->vm_start, &ilx); > - if (pol && (pol->flags & MPOL_F_MOF)) > - ret = true; > - mpol_cond_put(pol); > - > - return ret; > - } > - > - pol = vma->vm_policy; > + pol = __get_vma_policy(vma, vma->vm_start, &ilx); > if (!pol) > pol = get_task_policy(current); > - > - return pol->flags & MPOL_F_MOF; > + mof = pol->flags & MPOL_F_MOF; > + mpol_cond_put(pol); > + return mof; > } > > bool apply_policy_zone(struct mempolicy *policy, enum zone_type zone) > -- > The change to use the fallback seems reasonable Acked-by: Balbir Singh