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kwin/cmake/modules/FindLibcap.cmake

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Use real-time scheduling policy for kwin_wayland Summary: The base idea behind this change is to keep the system responsive no matter what other processes do. All input and rendering needs to go through the windowing system, so keeping it responsive is important. Currently KWin competes with all other processes for resources and this can render the system unusable. Consider some processes running amok. In this case the user might not be able to easily close the applications as KWin does not get the cpu time to perform the input tasks requested by the user. Or in the case of playing a demanding game it is important that KWin gets scheduled to forward the pointer input events. The user doesn't want that the game (or another process) wins against the windowing sytem. The disadvantage is that KWin always wins against other processes with real time scheduling. This could result in KWin running amok stalling the system. On the other hand this is no change to the current situation as if KWin runs amok the sytem is unusable. The change uses libcap to set CAP_SYS_NICE on kwin_wayland executable. KWin_wayland on start sets the scheduling policy to SCHED_RR with the lowest possible priority. Thus any other SCHED_RR process will win against KWin. So real time processes are not affected by this change! After adjusting the scheduling (which requires CAP_SYS_NICE) KWin drops this capability again. Test Plan: Verified that KWin adjusts the scheduler, that it is not passed to child processes, that the capability gets dropped and not passed to child processes. Reviewers: #kwin, #plasma Subscribers: plasma-devel, kwin Tags: #kwin Differential Revision: https://phabricator.kde.org/D7757
7 years ago
# Try to find the setcap binary and cap libraries
#
# This will define:
#
# Libcap_FOUND - system has the cap library and setcap binary
# Libcap_LIBRARIES - cap libraries to link against
# SETCAP_EXECUTABLE - path of the setcap binary
# In addition, the following targets are defined:
#
# Libcap::SetCapabilities
#
Switch to SPDX license markers The main advantage of SPDX license identifiers over the traditional license headers is that it's more difficult to overlook inappropriate licenses for kwin, for example GPL 3. We also don't have to copy a lot of boilerplate text. In order to create this change, I ran licensedigger -r -c from the toplevel source directory.
4 years ago
# SPDX-FileCopyrightText: 2014 Hrvoje Senjan <hrvoje.senjan@gmail.com>
Use real-time scheduling policy for kwin_wayland Summary: The base idea behind this change is to keep the system responsive no matter what other processes do. All input and rendering needs to go through the windowing system, so keeping it responsive is important. Currently KWin competes with all other processes for resources and this can render the system unusable. Consider some processes running amok. In this case the user might not be able to easily close the applications as KWin does not get the cpu time to perform the input tasks requested by the user. Or in the case of playing a demanding game it is important that KWin gets scheduled to forward the pointer input events. The user doesn't want that the game (or another process) wins against the windowing sytem. The disadvantage is that KWin always wins against other processes with real time scheduling. This could result in KWin running amok stalling the system. On the other hand this is no change to the current situation as if KWin runs amok the sytem is unusable. The change uses libcap to set CAP_SYS_NICE on kwin_wayland executable. KWin_wayland on start sets the scheduling policy to SCHED_RR with the lowest possible priority. Thus any other SCHED_RR process will win against KWin. So real time processes are not affected by this change! After adjusting the scheduling (which requires CAP_SYS_NICE) KWin drops this capability again. Test Plan: Verified that KWin adjusts the scheduler, that it is not passed to child processes, that the capability gets dropped and not passed to child processes. Reviewers: #kwin, #plasma Subscribers: plasma-devel, kwin Tags: #kwin Differential Revision: https://phabricator.kde.org/D7757
7 years ago
#
Switch to SPDX license markers The main advantage of SPDX license identifiers over the traditional license headers is that it's more difficult to overlook inappropriate licenses for kwin, for example GPL 3. We also don't have to copy a lot of boilerplate text. In order to create this change, I ran licensedigger -r -c from the toplevel source directory.
4 years ago
# SPDX-License-Identifier: BSD-3-Clause
Use real-time scheduling policy for kwin_wayland Summary: The base idea behind this change is to keep the system responsive no matter what other processes do. All input and rendering needs to go through the windowing system, so keeping it responsive is important. Currently KWin competes with all other processes for resources and this can render the system unusable. Consider some processes running amok. In this case the user might not be able to easily close the applications as KWin does not get the cpu time to perform the input tasks requested by the user. Or in the case of playing a demanding game it is important that KWin gets scheduled to forward the pointer input events. The user doesn't want that the game (or another process) wins against the windowing sytem. The disadvantage is that KWin always wins against other processes with real time scheduling. This could result in KWin running amok stalling the system. On the other hand this is no change to the current situation as if KWin runs amok the sytem is unusable. The change uses libcap to set CAP_SYS_NICE on kwin_wayland executable. KWin_wayland on start sets the scheduling policy to SCHED_RR with the lowest possible priority. Thus any other SCHED_RR process will win against KWin. So real time processes are not affected by this change! After adjusting the scheduling (which requires CAP_SYS_NICE) KWin drops this capability again. Test Plan: Verified that KWin adjusts the scheduler, that it is not passed to child processes, that the capability gets dropped and not passed to child processes. Reviewers: #kwin, #plasma Subscribers: plasma-devel, kwin Tags: #kwin Differential Revision: https://phabricator.kde.org/D7757
7 years ago
find_program(SETCAP_EXECUTABLE NAMES setcap DOC "The setcap executable")
find_library(Libcap_LIBRARIES NAMES cap DOC "The cap (capabilities) library")
include(FindPackageHandleStandardArgs)
find_package_handle_standard_args(Libcap FOUND_VAR Libcap_FOUND
REQUIRED_VARS SETCAP_EXECUTABLE Libcap_LIBRARIES)
if(Libcap_FOUND AND NOT TARGET Libcap::SetCapabilities)
add_executable(Libcap::SetCapabilities IMPORTED)
set_target_properties(Libcap::SetCapabilities PROPERTIES
IMPORTED_LOCATION "${SETCAP_EXECUTABLE}"
)
endif()
mark_as_advanced(SETCAP_EXECUTABLE Libcap_LIBRARIES)
include(FeatureSummary)
set_package_properties(Libcap PROPERTIES
URL https://sites.google.com/site/fullycapable/
DESCRIPTION "Capabilities are a measure to limit the omnipotence of the superuser.")