On Wed, Sep 30, 2020 at 10:21:17PM +0000, Kalesh Singh wrote: > mremap time can be optimized by moving entries at the PMD/PUD level if > the source and destination addresses are PMD/PUD-aligned and > PMD/PUD-sized. Enable moving at the PMD and PUD levels on arm64 and > x86. Other architectures where this type of move is supported and known to > be safe can also opt-in to these optimizations by enabling HAVE_MOVE_PMD > and HAVE_MOVE_PUD. > > Observed Performance Improvements for remapping a PUD-aligned 1GB-sized > region on x86 and arm64: > > - HAVE_MOVE_PMD is already enabled on x86 : N/A > - Enabling HAVE_MOVE_PUD on x86 : ~13x speed up > > - Enabling HAVE_MOVE_PMD on arm64 : ~ 8x speed up > - Enabling HAVE_MOVE_PUD on arm64 : ~19x speed up > > Altogether, HAVE_MOVE_PMD and HAVE_MOVE_PUD > give a total of ~150x speed up on arm64. Is there a *real* workload that benefit from HAVE_MOVE_PUD? -- Kirill A. Shutemov
