diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 4 | ||||
| -rw-r--r-- | Documentation/arm64/silicon-errata.rst | 2 | ||||
| -rw-r--r-- | Documentation/scheduler/sched-bwc.rst | 74 | ||||
| -rw-r--r-- | Documentation/usb/rio.rst | 109 |
4 files changed, 66 insertions, 123 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 4c1971960afa..5ea005c9e2d6 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5267,6 +5267,10 @@ the unplug protocol never -- do not unplug even if version check succeeds + xen_legacy_crash [X86,XEN] + Crash from Xen panic notifier, without executing late + panic() code such as dumping handler. + xen_nopvspin [X86,XEN] Disables the ticketlock slowpath using Xen PV optimizations. diff --git a/Documentation/arm64/silicon-errata.rst b/Documentation/arm64/silicon-errata.rst index 3e57d09246e6..6e52d334bc55 100644 --- a/Documentation/arm64/silicon-errata.rst +++ b/Documentation/arm64/silicon-errata.rst @@ -107,6 +107,8 @@ stable kernels. +----------------+-----------------+-----------------+-----------------------------+ | Cavium | ThunderX2 SMMUv3| #126 | N/A | +----------------+-----------------+-----------------+-----------------------------+ +| Cavium | ThunderX2 Core | #219 | CAVIUM_TX2_ERRATUM_219 | ++----------------+-----------------+-----------------+-----------------------------+ +----------------+-----------------+-----------------+-----------------------------+ | Freescale/NXP | LS2080A/LS1043A | A-008585 | FSL_ERRATUM_A008585 | +----------------+-----------------+-----------------+-----------------------------+ diff --git a/Documentation/scheduler/sched-bwc.rst b/Documentation/scheduler/sched-bwc.rst index 3a9064219656..9801d6b284b1 100644 --- a/Documentation/scheduler/sched-bwc.rst +++ b/Documentation/scheduler/sched-bwc.rst @@ -9,15 +9,16 @@ CFS bandwidth control is a CONFIG_FAIR_GROUP_SCHED extension which allows the specification of the maximum CPU bandwidth available to a group or hierarchy. The bandwidth allowed for a group is specified using a quota and period. Within -each given "period" (microseconds), a group is allowed to consume only up to -"quota" microseconds of CPU time. When the CPU bandwidth consumption of a -group exceeds this limit (for that period), the tasks belonging to its -hierarchy will be throttled and are not allowed to run again until the next -period. - -A group's unused runtime is globally tracked, being refreshed with quota units -above at each period boundary. As threads consume this bandwidth it is -transferred to cpu-local "silos" on a demand basis. The amount transferred +each given "period" (microseconds), a task group is allocated up to "quota" +microseconds of CPU time. That quota is assigned to per-cpu run queues in +slices as threads in the cgroup become runnable. Once all quota has been +assigned any additional requests for quota will result in those threads being +throttled. Throttled threads will not be able to run again until the next +period when the quota is replenished. + +A group's unassigned quota is globally tracked, being refreshed back to +cfs_quota units at each period boundary. As threads consume this bandwidth it +is transferred to cpu-local "silos" on a demand basis. The amount transferred within each of these updates is tunable and described as the "slice". Management @@ -35,12 +36,12 @@ The default values are:: A value of -1 for cpu.cfs_quota_us indicates that the group does not have any bandwidth restriction in place, such a group is described as an unconstrained -bandwidth group. This represents the traditional work-conserving behavior for +bandwidth group. This represents the traditional work-conserving behavior for CFS. Writing any (valid) positive value(s) will enact the specified bandwidth limit. -The minimum quota allowed for the quota or period is 1ms. There is also an -upper bound on the period length of 1s. Additional restrictions exist when +The minimum quota allowed for the quota or period is 1ms. There is also an +upper bound on the period length of 1s. Additional restrictions exist when bandwidth limits are used in a hierarchical fashion, these are explained in more detail below. @@ -53,8 +54,8 @@ unthrottled if it is in a constrained state. System wide settings -------------------- For efficiency run-time is transferred between the global pool and CPU local -"silos" in a batch fashion. This greatly reduces global accounting pressure -on large systems. The amount transferred each time such an update is required +"silos" in a batch fashion. This greatly reduces global accounting pressure +on large systems. The amount transferred each time such an update is required is described as the "slice". This is tunable via procfs:: @@ -97,6 +98,51 @@ There are two ways in which a group may become throttled: In case b) above, even though the child may have runtime remaining it will not be allowed to until the parent's runtime is refreshed. +CFS Bandwidth Quota Caveats +--------------------------- +Once a slice is assigned to a cpu it does not expire. However all but 1ms of +the slice may be returned to the global pool if all threads on that cpu become +unrunnable. This is configured at compile time by the min_cfs_rq_runtime +variable. This is a performance tweak that helps prevent added contention on +the global lock. + +The fact that cpu-local slices do not expire results in some interesting corner +cases that should be understood. + +For cgroup cpu constrained applications that are cpu limited this is a +relatively moot point because they will naturally consume the entirety of their +quota as well as the entirety of each cpu-local slice in each period. As a +result it is expected that nr_periods roughly equal nr_throttled, and that +cpuacct.usage will increase roughly equal to cfs_quota_us in each period. + +For highly-threaded, non-cpu bound applications this non-expiration nuance +allows applications to briefly burst past their quota limits by the amount of +unused slice on each cpu that the task group is running on (typically at most +1ms per cpu or as defined by min_cfs_rq_runtime). This slight burst only +applies if quota had been assigned to a cpu and then not fully used or returned +in previous periods. This burst amount will not be transferred between cores. +As a result, this mechanism still strictly limits the task group to quota +average usage, albeit over a longer time window than a single period. This +also limits the burst ability to no more than 1ms per cpu. This provides +better more predictable user experience for highly threaded applications with +small quota limits on high core count machines. It also eliminates the +propensity to throttle these applications while simultanously using less than +quota amounts of cpu. Another way to say this, is that by allowing the unused +portion of a slice to remain valid across periods we have decreased the +possibility of wastefully expiring quota on cpu-local silos that don't need a +full slice's amount of cpu time. + +The interaction between cpu-bound and non-cpu-bound-interactive applications +should also be considered, especially when single core usage hits 100%. If you +gave each of these applications half of a cpu-core and they both got scheduled +on the same CPU it is theoretically possible that the non-cpu bound application +will use up to 1ms additional quota in some periods, thereby preventing the +cpu-bound application from fully using its quota by that same amount. In these +instances it will be up to the CFS algorithm (see sched-design-CFS.rst) to +decide which application is chosen to run, as they will both be runnable and +have remaining quota. This runtime discrepancy will be made up in the following +periods when the interactive application idles. + Examples -------- 1. Limit a group to 1 CPU worth of runtime:: diff --git a/Documentation/usb/rio.rst b/Documentation/usb/rio.rst deleted file mode 100644 index ea73475471db..000000000000 --- a/Documentation/usb/rio.rst +++ /dev/null @@ -1,109 +0,0 @@ -============ -Diamonds Rio -============ - -Copyright (C) 1999, 2000 Bruce Tenison - -Portions Copyright (C) 1999, 2000 David Nelson - -Thanks to David Nelson for guidance and the usage of the scanner.txt -and scanner.c files to model our driver and this informative file. - -Mar. 2, 2000 - -Changes -======= - -- Initial Revision - - -Overview -======== - -This README will address issues regarding how to configure the kernel -to access a RIO 500 mp3 player. -Before I explain how to use this to access the Rio500 please be warned: - -.. warning:: - - Please note that this software is still under development. The authors - are in no way responsible for any damage that may occur, no matter how - inconsequential. - -It seems that the Rio has a problem when sending .mp3 with low batteries. -I suggest when the batteries are low and you want to transfer stuff that you -replace it with a fresh one. In my case, what happened is I lost two 16kb -blocks (they are no longer usable to store information to it). But I don't -know if that's normal or not; it could simply be a problem with the flash -memory. - -In an extreme case, I left my Rio playing overnight and the batteries wore -down to nothing and appear to have corrupted the flash memory. My RIO -needed to be replaced as a result. Diamond tech support is aware of the -problem. Do NOT allow your batteries to wear down to nothing before -changing them. It appears RIO 500 firmware does not handle low battery -power well at all. - -On systems with OHCI controllers, the kernel OHCI code appears to have -power on problems with some chipsets. If you are having problems -connecting to your RIO 500, try turning it on first and then plugging it -into the USB cable. - -Contact Information -------------------- - - The main page for the project is hosted at sourceforge.net in the following - URL: <http://rio500.sourceforge.net>. You can also go to the project's - sourceforge home page at: <http://sourceforge.net/projects/rio500/>. - There is also a mailing list: rio500-users@lists.sourceforge.net - -Authors -------- - -Most of the code was written by Cesar Miquel <miquel@df.uba.ar>. Keith -Clayton <kclayton@jps.net> is incharge of the PPC port and making sure -things work there. Bruce Tenison <btenison@dibbs.net> is adding support -for .fon files and also does testing. The program will mostly sure be -re-written and Pete Ikusz along with the rest will re-design it. I would -also like to thank Tri Nguyen <tmn_3022000@hotmail.com> who provided use -with some important information regarding the communication with the Rio. - -Additional Information and userspace tools - - http://rio500.sourceforge.net/ - - -Requirements -============ - -A host with a USB port running a Linux kernel with RIO 500 support enabled. - -The driver is a module called rio500, which should be automatically loaded -as you plug in your device. If that fails you can manually load it with - - modprobe rio500 - -Udev should automatically create a device node as soon as plug in your device. -If that fails, you can manually add a device for the USB rio500:: - - mknod /dev/usb/rio500 c 180 64 - -In that case, set appropriate permissions for /dev/usb/rio500 (don't forget -about group and world permissions). Both read and write permissions are -required for proper operation. - -That's it. The Rio500 Utils at: http://rio500.sourceforge.net should -be able to access the rio500. - -Limits -====== - -You can use only a single rio500 device at a time with your computer. - -Bugs -==== - -If you encounter any problems feel free to drop me an email. - -Bruce Tenison -btenison@dibbs.net |