realtime:documentation:known_limitations
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| Both sides previous revision Previous revision Next revision | Previous revision | ||
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realtime:documentation:known_limitations [2017/05/19 09:57] anna-maria insert feature request page, because it is as well a known limitation |
realtime:documentation:known_limitations [2023/10/02 20:16] (current) costa.shul - elixir |
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| ===== Disabled CONFIG_ options ===== | ===== Disabled CONFIG_ options ===== | ||
| - | Several features are disabled by CONFIG_PREEMPT_RT_FULL=y because of incompatibility. | + | Several features are disabled by CONFIG_PREEMPT_RT=y because of incompatibility. |
| <WRAP center round todo 80%> | <WRAP center round todo 80%> | ||
| Line 15: | Line 15: | ||
| * CONFIG_TRANSPARENT_HUGEPAGE | * CONFIG_TRANSPARENT_HUGEPAGE | ||
| - | * CONFIG_OPROFILE | + | * CONFIG_DRM_I915 |
| - | * CONFIG_XEN (arm64) | + | * CONFIG_NUMA_BALANCING |
| - | * CONFIG_X86_POWERNOW_K8 | + | * CONFIG_LEDS_TRIGGER_CPU |
| - | * CONFIG_BCACHE | + | |
| - | * CONFIG_HIGHMEM (mips, powerpc) | + | |
| * CONFIG_KVM_MPIC (powerpc) | * CONFIG_KVM_MPIC (powerpc) | ||
| - | * CONFIG_RT_GROUP_SCHED | + | * CONFIG_OPROFILE (until v5.12-rc2-rt1) |
| - | * CONFIG_CPUMASK_OFFSTACK | + | * CONFIG_XEN (until v4.18-rc8-rt1) |
| + | * CONFIG_X86_POWERNOW_K8 (until v5.2.21-rt13) | ||
| + | * CONFIG_BCACHE (until v5.6.17-rt10) | ||
| + | * CONFIG_HIGHMEM (mips, powerpc, until v5.10-rc1-rt2) | ||
| + | * CONFIG_RT_GROUP_SCHED (until v5.15-rc2-rt3) | ||
| + | * CONFIG_CPUMASK_OFFSTACK (until 5.4.5-rt3) | ||
| ===== Platforms ===== | ===== Platforms ===== | ||
| Line 48: | Line 50: | ||
| The //pthread_cond_t// variable in glibc implementation contains a mutex. This mutex can not be initialized as PI. | The //pthread_cond_t// variable in glibc implementation contains a mutex. This mutex can not be initialized as PI. | ||
| More information can be found in [[https://sourceware.org/bugzilla/show_bug.cgi?id=11588|glibc's bug report]]. | More information can be found in [[https://sourceware.org/bugzilla/show_bug.cgi?id=11588|glibc's bug report]]. | ||
| + | |||
| + | ==== EFI ==== | ||
| + | [[https://elixir.bootlin.com/linux/latest/A/ident/CONFIG_EFI_DISABLE_RUNTIME|EFI runtime services are disabled]] because using them may case high latencies. This includes accessing the RTC device or updating the variables. | ||
| + | If you need to use the EFI runtime services add **efi=runtime** to the kernel command line. | ||
| + | |||
| + | ==== Memory compaction ==== | ||
| + | With CONFIG_COMPACTION=y the kernel may change the physical address for an existing virtual address. This may lead to a minor page fault and may happen even to pages which are protected with //mlock()//. | ||
| + | In order to avoid memory compaction on //mlock()// pages exclude them via | ||
| + | |||
| + | echo 0 > /proc/sys/vm/compact_unevictable_allowed | ||
realtime/documentation/known_limitations.1495187848.txt.gz · Last modified: 2017/05/19 09:57 by anna-maria
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