Transparent hugepages should default to enabled=madvise

Bug #1703742 reported by Nelson Elhage on 2017-07-12
14
This bug affects 2 people
Affects Status Importance Assigned to Milestone
linux (Ubuntu)
Status tracked in Artful
Xenial
Undecided
Colin Ian King
Yakkety
Undecided
Unassigned
Zesty
Undecided
Colin Ian King
Artful
High
Colin Ian King
linux-gke (Ubuntu)
Undecided
Kamal Mostafa
Xenial
Undecided
Kamal Mostafa

Bug Description

Ubuntu kernels should default transparent_hugepages to enabled=madvise, not enabled=always

(this corresponds to TRANSPARENT_HUGEPAGE_MADVISE=y in .config).

I've blogged about this at some length here: https://blog.nelhage.com/post/transparent-hugepages/ but here is a summary:

Transparent Hugepages are a feature that allows the kernel to attempt to automatically back any anonymous maps with "huge" 2MiB page tables, instead of the normal 4k entries. It can produce small net performance gains in certain benchmarks, but also has numerous downsides, in the form of apparent memory leaks and 30% slowdowns or worse for some applications. Many popular pieces of software now refuse to run with hugepages enabled because of known performance issues.

Examples of problem reports:
MongoDB: https://docs.mongodb.com/manual/tutorial/transparent-huge-pages/
Oracle: https://blogs.oracle.com/linux/entry/performance_issues_with_transparent_huge
Splunk: https://docs.splunk.com/Documentation/Splunk/6.5.2/ReleaseNotes/SplunkandTHP
Go runtime: https://github.com/golang/go/issues/8832
jemalloc: https://blog.digitalocean.com/transparent-huge-pages-and-alternative-memory-allocators/
node.js: https://github.com/nodejs/node/issues/11077

Setting `enabled=madvise` enables applications that know they benefit from transparent huge pages to opt-in to this feature, while eliminating all the problematic behavior for other applications. Note also that transparent hugepage settings don't affect the use of explicit hugepages via hugetlbfs or mmap(…, MAP_HUGETLB, …)

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1703742

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

Changed in linux (Ubuntu):
status: New → Incomplete
Colin Ian King (colin-king) wrote :

Thank you for reporting this. I'm currently evaluating this with some benchmarking experiments and my current observation concurs with the observations. I believe enabled=madvise is probably the best way forward but I still have several more test scenarios to complete to ensure we don't hit any unexpected performance regresions.

Changed in linux (Ubuntu):
status: Incomplete → In Progress
importance: Undecided → High
assignee: nobody → Colin Ian King (colin-king)
Seth Forshee (sforshee) on 2017-07-13
Changed in linux (Ubuntu Artful):
status: In Progress → Fix Committed
Colin Ian King (colin-king) wrote :

Note: Current plan is to see how this works on Artful and SRU these once we are happy with the results in Artful.

This bug was nominated against a series that is no longer supported, ie yakkety. The bug task representing the yakkety nomination is being closed as Won't Fix.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

Changed in linux (Ubuntu Yakkety):
status: New → Won't Fix
Launchpad Janitor (janitor) wrote :
Download full text (24.9 KiB)

This bug was fixed in the package linux - 4.11.0-13.19

---------------
linux (4.11.0-13.19) artful; urgency=low

  * CVE-2017-7533
    - dentry name snapshots

linux (4.11.0-12.18) artful; urgency=low

  * linux: 4.11.0-12.18 -proposed tracker (LP: #1707635)
    - no change rebuild to pick up the new binutils.

  * Adt tests of src:linux time out often on armhf lxc containers (LP: #1705495)
    - [Packaging] tests -- reduce rebuild test to one flavour
    - [Packaging] tests -- reduce rebuild test to one flavour -- use filter

  * [ARM64] config EDAC_GHES=y depends on EDAC_MM_EDAC=y (LP: #1706141)
    - [Config] set EDAC_MM_EDAC=y for ARM64

  * [Hyper-V] hv_netvsc: Exclude non-TCP port numbers from vRSS hashing
    (LP: #1690174)
    - hv_netvsc: Exclude non-TCP port numbers from vRSS hashing

  * ath10k doesn't report full RSSI information (LP: #1706531)
    - ath10k: add per chain RSSI reporting

  * ideapad_laptop don't support v310-14isk (LP: #1705378)
    - platform/x86: ideapad-laptop: Add several models to no_hw_rfkill

  * Ubuntu 16.04.3: Qemu fails on P9 (LP: #1686019)
    - KVM: PPC: Pass kvm* to kvmppc_find_table()
    - KVM: PPC: Use preregistered memory API to access TCE list
    - KVM: PPC: VFIO: Add in-kernel acceleration for VFIO
    - powerpc/powernv/iommu: Add real mode version of iommu_table_ops::exchange()
    - powerpc/iommu/vfio_spapr_tce: Cleanup iommu_table disposal
    - powerpc/vfio_spapr_tce: Add reference counting to iommu_table
    - powerpc/mmu: Add real mode support for IOMMU preregistered memory
    - KVM: PPC: Reserve KVM_CAP_SPAPR_TCE_VFIO capability number
    - KVM: PPC: Book3S HV: Add radix checks in real-mode hypercall handlers

  * hns: ethtool selftest crashes system (LP: #1705712)
    - net/hns:bugfix of ethtool -t phy self_test

  * ThunderX: soft lockup on 4.8+ kernels when running qemu-efi with vhost=on
    (LP: #1673564)
    - KVM: arm/arm64: vgic-v3: Use PREbits to infer the number of ICH_APxRn_EL2
      registers
    - KVM: arm/arm64: vgic-v3: Fix nr_pre_bits bitfield extraction
    - arm64: Add a facility to turn an ESR syndrome into a sysreg encoding
    - KVM: arm/arm64: vgic-v3: Add accessors for the ICH_APxRn_EL2 registers
    - KVM: arm64: Make kvm_condition_valid32() accessible from EL2
    - KVM: arm64: vgic-v3: Add hook to handle guest GICv3 sysreg accesses at EL2
    - KVM: arm64: vgic-v3: Add ICV_BPR1_EL1 handler
    - KVM: arm64: vgic-v3: Add ICV_IGRPEN1_EL1 handler
    - KVM: arm64: vgic-v3: Add ICV_IAR1_EL1 handler
    - KVM: arm64: vgic-v3: Add ICV_EOIR1_EL1 handler
    - KVM: arm64: vgic-v3: Add ICV_AP1Rn_EL1 handler
    - KVM: arm64: vgic-v3: Add ICV_HPPIR1_EL1 handler
    - KVM: arm64: vgic-v3: Enable trapping of Group-1 system registers
    - KVM: arm64: Enable GICv3 Group-1 sysreg trapping via command-line
    - KVM: arm64: vgic-v3: Add ICV_BPR0_EL1 handler
    - KVM: arm64: vgic-v3: Add ICV_IGNREN0_EL1 handler
    - KVM: arm64: vgic-v3: Add misc Group-0 handlers
    - KVM: arm64: vgic-v3: Enable trapping of Group-0 system registers
    - KVM: arm64: Enable GICv3 Group-0 sysreg trapping via command-line
    - arm64: Add MIDR values for Cavium cn83XX SoCs
    - arm64: Add wor...

Changed in linux (Ubuntu Artful):
status: Fix Committed → Fix Released
Changed in linux (Ubuntu Xenial):
assignee: nobody → Colin Ian King (colin-king)
Changed in linux (Ubuntu Zesty):
assignee: nobody → Colin Ian King (colin-king)
Changed in linux (Ubuntu Xenial):
status: New → In Progress
Changed in linux (Ubuntu Zesty):
status: New → In Progress
no longer affects: linux-gke (Ubuntu Yakkety)
no longer affects: linux-gke (Ubuntu Zesty)
no longer affects: linux-gke (Ubuntu Artful)
Changed in linux-gke (Ubuntu Xenial):
status: New → Fix Committed
assignee: nobody → Kamal Mostafa (kamalmostafa)
Changed in linux-gke (Ubuntu):
status: New → Fix Committed
assignee: nobody → Kamal Mostafa (kamalmostafa)
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