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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 May 2023 18:16:50.2174 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: c6067a43-e948-42b5-cbad-08db5702e263 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[63.35.35.123];Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com] X-MS-Exchange-CrossTenant-AuthSource: AM7EUR03FT043.eop-EUR03.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PAXPR08MB6446 X-Spam-Status: No, score=-4.9 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,FORGED_SPF_HELO,KAM_DMARC_NONE,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_PASS,SPF_NONE,TXREP,T_SCC_BODY_TEXT_LINE,UNPARSEABLE_RELAY autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: Hi Adhemerval,=0A= =0A= > But the threads themselves do not end up using all the VMA region allocat= ed=0A= > for them.=A0 Using the test program you can see it:=0A= =0A= Obviously that is due to there being a 2MB gap between each stack. After th= e=0A= huge page there is a default page for the guard and then empty space for th= e=0A= alignment till the next stack.=0A= =0A= > So even if the stack is not aligned to default large page, THP will still= =0A= > back up the thread allocation.=0A= =0A= THP can only be used if the mmap covers an aligned huge page. If you=0A= allocate lots of 2MB stacks then you get threads * guardsize / 2MB number= =0A= of huge pages since some stacks will become aligned.=0A= =0A= >The issues is, if the mmap is also aligned =0A= > to THP size, the guard setup will trigger the issue that will increase RS= S.=0A= =0A= No it won't. If it is aligned it will get a huge page, and the guard will b= e before=0A= the huge page (since we allocate 2MB + guardsize).=0A= =0A= > This seems to be same conclusion OpenJVM and some kernel discussion has= =0A= > reached as well [1] [2].=0A= =0A= If that is what they claim, they are wrong. This is not how THP or our stac= k=0A= allocation works. You can see the allocation of the THP and guard pages=0A= if you print the smaps (build with -DPRINT_PROC_SMAPS).=0A= =0A= Cheers,=0A= Wilco=