Messages in this thread |  | | Subject | Re: [PATCH V4] mm/vmstat: Add events for THP migration without split | From | John Hubbard <> | Date | Thu, 9 Jul 2020 13:15:15 -0700 |
| |
On 2020-07-09 10:42, Zi Yan wrote: ... > diff --git a/Documentation/vm/page_migration.rst b/Documentation/vm/page_migration.rst > index e65d49f3cf86..68883ac485fa 100644 > --- a/Documentation/vm/page_migration.rst > +++ b/Documentation/vm/page_migration.rst > @@ -253,24 +253,32 @@ which are function pointers of struct address_space_operations. > PG_isolated is alias with PG_reclaim flag so driver shouldn't use the flag > for own purpose. > > -Quantifying Migration > +Monitoring Migration > ===================== > -Following events can be used to quantify page migration. > - > -1. PGMIGRATE_SUCCESS /* Normal page migration success */ > -2. PGMIGRATE_FAIL /* Normal page migration failure */ > -3. THP_MIGRATION_SUCCESS /* Transparent huge page migration success */ > -4. THP_MIGRATION_FAILURE /* Transparent huge page migration failure */ > -5. THP_MIGRATION_SPLIT /* Transparent huge page got split, retried */ > - > -THP_MIGRATION_SUCCESS is when THP is migrated successfully without getting > -split into it's subpages. THP_MIGRATION_FAILURE is when THP could neither > -be migrated nor be split. THP_MIGRATION_SPLIT is when THP could not > -just be migrated as is but instead get split into it's subpages and later > -retried as normal pages. THP events would also update normal page migration > -statistics PGMIGRATE_SUCCESS and PGMIGRATE_FAILURE. These events will help > -in quantifying and analyzing various THP migration events including both > -success and failure cases. > + > +The following events (counters) can be used to monitor page migration. > + > +1. PGMIGRATE_SUCCESS: Normal page migration success. Each count means that a > + page was migrated. If the page was a non-THP page, then this counter is > + increased by one. If the page was a THP, then this counter is increased by > + the number of THP subpages. For example, migration of a single 2MB THP that > + has 4KB-size base pages (subpages) will cause this counter to increase by > + 512. > + > +2. PGMIGRATE_FAIL: Normal page migration failure. Same counting rules as for > + _SUCCESS, above: this will be increased by the number of subpages, if it was > + a THP. > + > +3. THP_MIGRATION_SUCCESS: A THP was migrated without being split. > + > +4. THP_MIGRATION_FAIL: A THP could not be migrated nor it could be split. > + > +5. THP_MIGRATION_SPLIT: A THP was migrated, but not as such: first, the THP had > + to be split. After splitting, a migration retry was used for it's sub-pages.
Just a documentation nit: "its sub-pages", not "it's sub-pages".
thanks, -- John Hubbard NVIDIA
|  |