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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Dec 2025 10:08:47.9166 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 011caa38-cf88-486a-31de-08de3e1d6f94 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[4.158.2.129];Helo=[outbound-uk1.az.dlp.m.darktrace.com] X-MS-Exchange-CrossTenant-AuthSource: DB1PEPF00039232.eurprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: VE1PR08MB5583 Hi David, > On 12/18/25 10:31, Yeoreum Yun wrote: > > Hi David, > > > > > On 12/18/25 09:37, Yeoreum Yun wrote: > > > > [...] > > > > > > I think it would be better to use only __GFP_HIGH in here since > > > > > > when kpti_install_ng_mappings() is called, "kswpd" doesn't created yet. > > > > > > and to allocate page with assurance, It would be good to use > > > > > > min_reserved to. > > > > > > > > > > > > Am I missing something? > > > > > > > > > > Personally I think we should just use "GFP_KERNEL | __GFP_ZERO". Anything else > > > > > would make this allocation look special, which it is not. If we fail to allocate > > > > > at this point in boot, we have bigger problems. > > > > > > > > But I'm not sure *HOW effective* to use GFP_KERNEL in here. > > > > Since it's before the any filesystem inited. > > > > IOW, in this context, almost there would be no *page cache* > > > > and I think it seems meaningless to use "GFP_KERNEL" and "direct > > > > reclaim" > > > > > > > > So to get success for allocation, __GFP_HIGH | _GFP_ZERO seems much > > > > better. > > > > > > Unless there is a real reason to confuse readers why this is very special, > > > just go with "GFP_KERNEL | __GFP_ZERO", really. > > > > > > In particular if it doesn't matter in practice? Or does it and we are not > > > getting your point? > > > > My worries was > > - kpti_install_ng_mappings() is called while in "smp_init()" which is > > before creating the kswapd thread via module_init(). > > Just wondered whether it allows to call wakeup_kswapd() before > > kswapd is created. > > The buddy should really be able to deal with that, no? > > > > > - Similar reason kcompactd too. > > Same as well. Nope. buddy handles them. It was a past :) > > We cannot expect alloc API users to know about these hidden details to work > around them :) > > > > > - Just wonder how much direct reclaim is effecitve since > > when kpti_install_ng_mappings() called before each > > filesystem initialised where not much of page cache in usage. > > Right, but do you really think we would ever trigger that path? > > The default should always be GFP_KERNEL unless we have for very good reason > special demands. > > So, do you think in practice there is real value in NOT using GFP_KERNEL? :) In the *practical view*. Absoultely NOT since I don't think it reaches those codes. Okay. I'll change with GFP_KERNEL | __GFP_ZERO. Thanks! -- Sincerely, Yeoreum Yun