• Peter Xu's avatar
    mm: do page fault accounting in handle_mm_fault · bce617ed
    Peter Xu authored
    Patch series "mm: Page fault accounting cleanups", v5.
    
    This is v5 of the pf accounting cleanup series.  It originates from Gerald
    Schaefer's report on an issue a week ago regarding to incorrect page fault
    accountings for retried page fault after commit 4064b982 ("mm: allow
    VM_FAULT_RETRY for multiple times"):
    
      https://lore.kernel.org/lkml/20200610174811.44b94525@thinkpad/
    
    What this series did:
    
      - Correct page fault accounting: we do accounting for a page fault
        (no matter whether it's from #PF handling, or gup, or anything else)
        only with the one that completed the fault.  For example, page fault
        retries should not be counted in page fault counters.  Same to the
        perf events.
    
      - Unify definition of PERF_COUNT_SW_PAGE_FAULTS: currently this perf
        event is used in an adhoc way across different archs.
    
        Case (1): for many archs it's done at the entry of a page fault
        handler, so that it will also cover e.g.  errornous faults.
    
        Case (2): for some other archs, it is only accounted when the page
        fault is resolved successfully.
    
        Case (3): there're still quite some archs that have not enabled
        this perf event.
    
        Since this series will touch merely all the archs, we unify this
        perf event to always follow case (1), which is the one that makes most
        sense.  And since we moved the accounting into handle_mm_fault, the
        other two MAJ/MIN perf events are well taken care of naturally.
    
      - Unify definition of "major faults": the definition of "major
        fault" is slightly changed when used in accounting (not
        VM_FAULT_MAJOR).  More information in patch 1.
    
      - Always account the page fault onto the one that triggered the page
        fault.  This does not matter much for #PF handlings, but mostly for
        gup.  More information on this in patch 25.
    
    Patchset layout:
    
    Patch 1:     Introduced the accounting in handle_mm_fault(), not enabled.
    Patch 2-23:  Enable the new accounting for arch #PF handlers one by one.
    Patch 24:    Enable the new accounting for the rest outliers (gup, iommu, etc.)
    Patch 25:    Cleanup GUP task_struct pointer since it's not needed any more
    
    This patch (of 25):
    
    This is a preparation patch to move page fault accountings into the
    general code in handle_mm_fault().  This includes both the per task
    flt_maj/flt_min counters, and the major/minor page fault perf events.  To
    do this, the pt_regs pointer is passed into handle_mm_fault().
    
    PERF_COUNT_SW_PAGE_FAULTS should still be kept in per-arch page fault
    handlers.
    
    So far, all the pt_regs pointer that passed into handle_mm_fault() is
    NULL, which means this patch should have no intented functional change.
    Suggested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: default avatarPeter Xu <peterx@redhat.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Cc: Albert Ou <aou@eecs.berkeley.edu>
    Cc: Alexander Gordeev <agordeev@linux.ibm.com>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Brian Cain <bcain@codeaurora.org>
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Cc: Christian Borntraeger <borntraeger@de.ibm.com>
    Cc: Chris Zankel <chris@zankel.net>
    Cc: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: David S. Miller <davem@davemloft.net>
    Cc: Geert Uytterhoeven <geert@linux-m68k.org>
    Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
    Cc: Greentime Hu <green.hu@gmail.com>
    Cc: Guo Ren <guoren@kernel.org>
    Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
    Cc: Helge Deller <deller@gmx.de>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
    Cc: James E.J. Bottomley <James.Bottomley@HansenPartnership.com>
    Cc: John Hubbard <jhubbard@nvidia.com>
    Cc: Jonas Bonn <jonas@southpole.se>
    Cc: Ley Foon Tan <ley.foon.tan@intel.com>
    Cc: "Luck, Tony" <tony.luck@intel.com>
    Cc: Matt Turner <mattst88@gmail.com>
    Cc: Max Filippov <jcmvbkbc@gmail.com>
    Cc: Michael Ellerman <mpe@ellerman.id.au>
    Cc: Michal Simek <monstr@monstr.eu>
    Cc: Nick Hu <nickhu@andestech.com>
    Cc: Palmer Dabbelt <palmer@dabbelt.com>
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: Paul Walmsley <paul.walmsley@sifive.com>
    Cc: Pekka Enberg <penberg@kernel.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Richard Henderson <rth@twiddle.net>
    Cc: Rich Felker <dalias@libc.org>
    Cc: Russell King <linux@armlinux.org.uk>
    Cc: Stafford Horne <shorne@gmail.com>
    Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
    Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Vasily Gorbik <gor@linux.ibm.com>
    Cc: Vincent Chen <deanbo422@gmail.com>
    Cc: Vineet Gupta <vgupta@synopsys.com>
    Cc: Will Deacon <will@kernel.org>
    Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
    Link: http://lkml.kernel.org/r/20200707225021.200906-1-peterx@redhat.com
    Link: http://lkml.kernel.org/r/20200707225021.200906-2-peterx@redhat.comSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    bce617ed
fault.c 8.51 KB