Changelog since V4
o Rebase to 3.19-rc2 (mel)
Changelog since V3
o Minor comment update (benh)
o Add ack'ed bys
Changelog since V2
o Rename *_protnone_numa to _protnone and extend docs (linus)
o Rebase to mmotm-20141119 for pre-merge testing (mel)
o Conver WARN_ON to VM_WARN_ON (aneesh)
Changelog since V1
o ppc64 paranoia checks and clarifications (aneesh)
o Fix trinity regression (hopefully)
o Reduce unnecessary TLB flushes (mel)
Automatic NUMA balancing depends on protecting PTEs to trap a fault and
gather reference locality information. Very broadly speaking it marks PTEs
as not present and uses another bit to distinguish between NUMA hinting
faults and other types of faults. This approach is not universally loved,
ultimately resulted in swap space shrinking and has had a number of
problems with Xen support. This series is very heavily based on patches
from Linus and Aneesh to replace the existing PTE/PMD NUMA helper functions
with normal change protections that should be less problematic. This was
tested on a few different workloads that showed automatic NUMA balancing
was still active with mostly comparable results.
specjbb single JVM: There was negligible performance difference in the
benchmark itself for short runs. However, system activity is
higher and interrupts are much higher over time -- possibly TLB
flushes. Migrations are also higher. Overall, this is more overhead
but considering the problems faced with the old approach I think
we just have to suck it up and find another way of reducing the
overhead.
specjbb multi JVM: Negligible performance difference to the actual benchmark
but like the single JVM case, the system overhead is noticeably
higher. Again, interrupts are a major factor.
autonumabench: This was all over the place and about all that can be
reasonably concluded is that it's different but not necessarily
better or worse.
autonumabench
3.19.0-rc2 3.19.0-rc2
vanilla protnone-v5r1
Time System-NUMA01 268.99 ( 0.00%) 1350.70 (-402.14%)
Time System-NUMA01_THEADLOCAL 110.14 ( 0.00%) 50.68 ( 53.99%)
Time System-NUMA02 20.14 ( 0.00%) 31.12 (-54.52%)
Time System-NUMA02_SMT 7.40 ( 0.00%) 6.57 ( 11.22%)
Time Elapsed-NUMA01 687.57 ( 0.00%) 528.51 ( 23.13%)
Time Elapsed-NUMA01_THEADLOCAL 540.29 ( 0.00%) 554.36 ( -2.60%)
Time Elapsed-NUMA02 84.98 ( 0.00%) 78.87 ( 7.19%)
Time Elapsed-NUMA02_SMT 77.32 ( 0.00%) 87.07 (-12.61%)
System CPU usage of NUMA01 is worse but it's an adverse workload on this
machine so I'm reluctant to conclude that it's a problem that matters.
Overall time to complete the benchmark is comparable
3.19.0-rc2 3.19.0-rc2
vanillaprotnone-v5r1
User 58100.89 48351.17
System 407.74 1439.22
Elapsed 1411.44 1250.55
NUMA alloc hit 5398081 5536696
NUMA alloc miss 0 0
NUMA interleave hit 0 0
NUMA alloc local 5398073 5536668
NUMA base PTE updates 622722221 442576477
NUMA huge PMD updates 1215268 863690
NUMA page range updates 1244939437 884785757
NUMA hint faults 1696858 1221541
NUMA hint local faults 1046842 791219
NUMA hint local percent 61 64
NUMA pages migrated 6044430 59291698
The NUMA pages migrated look terrible but when I looked at a graph of the
activity over time I see that the massive spike in migration activity was
during NUMA01. This correlates with high system CPU usage and could be simply
down to bad luck but any modifications that affect that workload would be
related to scan rates and migrations, not the protection mechanism. For
all other workloads, migration activity was comparable.
Overall, headline performance figures are comparable but the overhead
is higher, mostly in interrupts. To some extent, higher overhead from
this approach was anticipated but not to this degree. It's going to be
necessary to reduce this again with a separate series in the future. It's
still worth going ahead with this series though as it's likely to avoid
constant headaches with Xen and is probably easier to maintain.
arch/powerpc/include/asm/pgtable.h | 54 ++----------
arch/powerpc/include/asm/pte-common.h | 5 --
arch/powerpc/include/asm/pte-hash64.h | 6 --
arch/powerpc/kvm/book3s_hv_rm_mmu.c | 2 +-
arch/powerpc/mm/copro_fault.c | 8 +-
arch/powerpc/mm/fault.c | 25 ++----
arch/powerpc/mm/pgtable.c | 11 ++-
arch/powerpc/mm/pgtable_64.c | 3 +-
arch/x86/include/asm/pgtable.h | 46 +++++-----
arch/x86/include/asm/pgtable_64.h | 5 --
arch/x86/include/asm/pgtable_types.h | 41 +--------
arch/x86/mm/gup.c | 4 +-
include/asm-generic/pgtable.h | 153 ++--------------------------------
include/linux/migrate.h | 4 -
include/linux/swapops.h | 2 +-
include/uapi/linux/mempolicy.h | 2 +-
mm/gup.c | 10 +--
mm/huge_memory.c | 50 ++++++-----
mm/memory.c | 18 ++--
mm/mempolicy.c | 2 +-
mm/migrate.c | 8 +-
mm/mprotect.c | 48 +++++------
mm/pgtable-generic.c | 2 -
23 files changed, 135 insertions(+), 374 deletions(-)
--
2.1.2
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