In-depth review of freshly baked Linux 3.6
The new core offers a hybrid backup feature, can cut off power to the “PCI” chip, and includes a new platform for user drivers. Other new features include security enhancements for the temporary catalog, as well as quotas and backups for Btrfs.
Linus Torvalds and his fellow developers took ten weeks to complete the now-released version of Linux 3.6. The new version, called "Terrified Chipmunk", offers a range of new features for both home users and professional system administrators.
Power management
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A new feature, Suspend to Both, provides Linux 3.6 with a hybrid backup capability. “Mac OS X” and “Windows” have been offering this feature for some time. This feature allows the computer to store data during sleep mode, both in RAM and on the system disk. Thus, a system that is in sleep mode will usually wake up within a few seconds, as if it is awakening from “Suspend-To-RAM” (ACPI S3), however, if during the sleep mode the power was lost (the battery went down) then the system will recover the RAM data from the hard disk, as well as after “Suspend-to-Disk” (Hibernate). In our short test with an older system and a 250 GB hard disk, Suspend-to-Both worked as expected. It took about 16 seconds to go to sleep - four times longer than with “Suspend-To-RAM” and as long as required for “Suspend-To-Disk”.
Linux kernel version 3.6 can send "PCIe" devices in the "D3cold" deep sleep state, this is supported by some modern computers to completely turn off individual "PCIe" devices.
File systems
The still-experimental “Btrfs” file system now supports quotas for specific areas within the file system. Another new feature in Btrfs is send / receive. It allows user programs to tell the difference between two snapshots (a snapshot of the file system), save these differences to a file, and restore backups as needed. This feature is especially useful for incremental, atomic backups. A more detailed description of this feature, which is also available on “ZFS”, can be found in the LWN.net article.
One of the new features implemented in “Linux 3.6” is based on the idea of 1996 — the kernel can now be configured not to follow hard and symbolic links in directories with a sticky bit set (such as / tmp /), These links point to folders above the directory tree. As LWN.net explains, this feature, which can be activated via Sysctl, put an end to the general technique that the attackers used to escalate privileges using background services running as administrator.
Storage
The new interface allows custom programs to notify the kernel when the size of a partition that they use changes, thereby allowing the kernel to know about changes in the size of mounted or other partitions at run time and act accordingly. The resizepart program, which uses the new interface, was included in the recently released second preliminary release of the version “Util-Linux 2.22-rc2”.
Changes in the software code “RAID” in the “MD” subsystem should improve the performance of the “RAID” arrays in which one or all storage devices are “SSD”. The kernel developers combined the “tcm_vhost” structural driver, which is classified as a statement, but does not live in a kernel tree setting. This allows SCSI devices on the host system to be used with minimal overhead for KVM virtual systems.
Virtualization
KVM now includes various modifications that reduce the load on interrupt handling and therefore increase performance. Another addition to the core is “IOMMU Groups”, which improves the isolation of “PCI” and “PCIe” devices using I / O virtualization technologies such as AMD-Vi and Intel VT-d. The “IOMMU Groups” function is also the basis for the “VFIO” (virtual I / O function - I / O). Designed primarily for KVM, this feature is designed to allow guests to access PCI and PCIe devices with low latency, high bandwidth levels and no risk to the host. Detailed information on VFIO is available in the documentation and described in the LWN.net article. Extensions that provide VFIO through QEMU are still under development.
Network
By default, “TCP Small Queues” (TSQ) allows Linux 3.6 to use small buffers of no more than 128 KB per network socket. Like other various recent changes to the kernel, this measure is intended to avoid “Bufferbloat” (excessive network buffering) - a term used for issues such as high network delays and connection failure caused by excessive buffering during data transfer. According to test results, smaller buffers per socket do not affect throughput. If necessary, administrators can use the file / proc / sys / net / ipv4 / tcp_limit_output_bytes to adjust the value at run time.
The kernel now includes TCP Fast Open (TFO) client support; The appearance of server support is planned in "Linux 3.7". TFO is an experimental extension of TCP, but has not yet been approved by the Internet Assigned Numbers Authority (IANA). It is designed to reduce the overhead of establishing a connection, which should speed up HTTP connections.
Drivers
The kernel developers combined a number of add-ons and fixed a bug in “Linux 3.6”, aimed at improving support for “Apple” - MacBooks released in July (such as “MacBook Pro Retina”). But still, not all the add-ons needed for the new MacBook have found their place in Linux 3.6. In addition, on some models, this version still causes problems during initialization or when using graphics hardware.
The Radeon graphics driver now activates the fastest “PCIe 2.0” transfer mode, where it is supported by hardware. Audio drivers now support Intel Haswell processors and their associated Lynx Point central controllers (PCH), which Intel plans to launch next year. The driver for the Lenovo's ThinkPad USB keyboard with the trackpoint was combined into an input subsystem.
The bnx2x driver, which processes Broadcom's various Ethernet chips, now supports the Energy-Efficient Ethernet (EEE) standard, which is defined in IEEE 802.3az. Users can now read or set “EEE” parameters using the recently released “Ethtool 3.5”.
Summarize
Btrfs has taken another step forward, and Linux finally offers proper support for hybrid expectations. Some system administrators will welcome new interfaces for the resizepart utility, because they allow you to modify existing partitions without the need to reboot the system. Improvements in protection regarding soft and hard links finally fixed many vulnerabilities.
Immediately after the release of “Linux 3.6”, as a rule, the “Linux” kernel development cycle begins again, during which kernel developers add many changes to the next version of the kernel to the main branch of development. Currently, numerous changes have already been prepared for the first phase of the next release.
Among the components ready for integration is the “Intel” graphics driver, which updates the code to install the on-screen modes. Also, the developers produce "overhaul" driver "Nouveau". Currently, it is not clear whether it will be integrated into “Linux 3.7”, or not. The same applies to "Aarch64" - 64-bit "ARM" architecture. Not so long ago, an article was published on LWN.net that provides an overview of the state of development of this project.
As usual, Kernel Log will summarize these and other events in the Linux kernel field — including new stable versions of the kernel (3.6.y), in which several errors missed by testers during development should be fixed in the next few weeks.
Linus Torvalds and his fellow developers took ten weeks to complete the now-released version of Linux 3.6. The new version, called "Terrified Chipmunk", offers a range of new features for both home users and professional system administrators.
Power management
')
A new feature, Suspend to Both, provides Linux 3.6 with a hybrid backup capability. “Mac OS X” and “Windows” have been offering this feature for some time. This feature allows the computer to store data during sleep mode, both in RAM and on the system disk. Thus, a system that is in sleep mode will usually wake up within a few seconds, as if it is awakening from “Suspend-To-RAM” (ACPI S3), however, if during the sleep mode the power was lost (the battery went down) then the system will recover the RAM data from the hard disk, as well as after “Suspend-to-Disk” (Hibernate). In our short test with an older system and a 250 GB hard disk, Suspend-to-Both worked as expected. It took about 16 seconds to go to sleep - four times longer than with “Suspend-To-RAM” and as long as required for “Suspend-To-Disk”.
Linux kernel version 3.6 can send "PCIe" devices in the "D3cold" deep sleep state, this is supported by some modern computers to completely turn off individual "PCIe" devices.
File systems
The still-experimental “Btrfs” file system now supports quotas for specific areas within the file system. Another new feature in Btrfs is send / receive. It allows user programs to tell the difference between two snapshots (a snapshot of the file system), save these differences to a file, and restore backups as needed. This feature is especially useful for incremental, atomic backups. A more detailed description of this feature, which is also available on “ZFS”, can be found in the LWN.net article.
One of the new features implemented in “Linux 3.6” is based on the idea of 1996 — the kernel can now be configured not to follow hard and symbolic links in directories with a sticky bit set (such as / tmp /), These links point to folders above the directory tree. As LWN.net explains, this feature, which can be activated via Sysctl, put an end to the general technique that the attackers used to escalate privileges using background services running as administrator.
Storage
The new interface allows custom programs to notify the kernel when the size of a partition that they use changes, thereby allowing the kernel to know about changes in the size of mounted or other partitions at run time and act accordingly. The resizepart program, which uses the new interface, was included in the recently released second preliminary release of the version “Util-Linux 2.22-rc2”.
Changes in the software code “RAID” in the “MD” subsystem should improve the performance of the “RAID” arrays in which one or all storage devices are “SSD”. The kernel developers combined the “tcm_vhost” structural driver, which is classified as a statement, but does not live in a kernel tree setting. This allows SCSI devices on the host system to be used with minimal overhead for KVM virtual systems.
Virtualization
KVM now includes various modifications that reduce the load on interrupt handling and therefore increase performance. Another addition to the core is “IOMMU Groups”, which improves the isolation of “PCI” and “PCIe” devices using I / O virtualization technologies such as AMD-Vi and Intel VT-d. The “IOMMU Groups” function is also the basis for the “VFIO” (virtual I / O function - I / O). Designed primarily for KVM, this feature is designed to allow guests to access PCI and PCIe devices with low latency, high bandwidth levels and no risk to the host. Detailed information on VFIO is available in the documentation and described in the LWN.net article. Extensions that provide VFIO through QEMU are still under development.
Network
By default, “TCP Small Queues” (TSQ) allows Linux 3.6 to use small buffers of no more than 128 KB per network socket. Like other various recent changes to the kernel, this measure is intended to avoid “Bufferbloat” (excessive network buffering) - a term used for issues such as high network delays and connection failure caused by excessive buffering during data transfer. According to test results, smaller buffers per socket do not affect throughput. If necessary, administrators can use the file / proc / sys / net / ipv4 / tcp_limit_output_bytes to adjust the value at run time.
The kernel now includes TCP Fast Open (TFO) client support; The appearance of server support is planned in "Linux 3.7". TFO is an experimental extension of TCP, but has not yet been approved by the Internet Assigned Numbers Authority (IANA). It is designed to reduce the overhead of establishing a connection, which should speed up HTTP connections.
Drivers
The kernel developers combined a number of add-ons and fixed a bug in “Linux 3.6”, aimed at improving support for “Apple” - MacBooks released in July (such as “MacBook Pro Retina”). But still, not all the add-ons needed for the new MacBook have found their place in Linux 3.6. In addition, on some models, this version still causes problems during initialization or when using graphics hardware.
The Radeon graphics driver now activates the fastest “PCIe 2.0” transfer mode, where it is supported by hardware. Audio drivers now support Intel Haswell processors and their associated Lynx Point central controllers (PCH), which Intel plans to launch next year. The driver for the Lenovo's ThinkPad USB keyboard with the trackpoint was combined into an input subsystem.
The bnx2x driver, which processes Broadcom's various Ethernet chips, now supports the Energy-Efficient Ethernet (EEE) standard, which is defined in IEEE 802.3az. Users can now read or set “EEE” parameters using the recently released “Ethtool 3.5”.
Summarize
Btrfs has taken another step forward, and Linux finally offers proper support for hybrid expectations. Some system administrators will welcome new interfaces for the resizepart utility, because they allow you to modify existing partitions without the need to reboot the system. Improvements in protection regarding soft and hard links finally fixed many vulnerabilities.
Immediately after the release of “Linux 3.6”, as a rule, the “Linux” kernel development cycle begins again, during which kernel developers add many changes to the next version of the kernel to the main branch of development. Currently, numerous changes have already been prepared for the first phase of the next release.
Among the components ready for integration is the “Intel” graphics driver, which updates the code to install the on-screen modes. Also, the developers produce "overhaul" driver "Nouveau". Currently, it is not clear whether it will be integrated into “Linux 3.7”, or not. The same applies to "Aarch64" - 64-bit "ARM" architecture. Not so long ago, an article was published on LWN.net that provides an overview of the state of development of this project.
As usual, Kernel Log will summarize these and other events in the Linux kernel field — including new stable versions of the kernel (3.6.y), in which several errors missed by testers during development should be fixed in the next few weeks.
Source: https://habr.com/ru/post/154315/
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