The setting of ops->dispatch_max_batch leads to a too large allocated
size for percpu allocator, and it will be unhappy if we want a size
larger than PCPU_MIN_UNIT_SIZE. Reduce MAX_ENQUEUED_TASKS for fix.
Implement a second-chance migration in select_cpu(): after a task has
been dispatched directly do not try to migrate it immediately on a
different CPU, but force it to stay on prev_cpu for another round.
This seems quite effective on certain architectures (such as on a system
with 11th Gen Intel(R) Core(TM) i7-1195G7 @ 2.90GHz), and it can provide
noticeable benefits with gaming or WebGL applications (such as
https://webglsamples.org/aquarium/aquarium.html) under regular workload
conditions (around +5% fps).
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Dispatch non-interactive tasks on the CPU selected by the built-in idle
selection logic and allow interactive tasks to be dispatched on any CPU.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
The shared DSQ is typically used to prioritize tasks and dispatch them
on the first CPU available, so consume from the shared DSQ before the
local CPU DSQ.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Do not always assign the maximum time slice to interactive tasks, but
use the same value of the dynamic time slice for everyone.
This seems to prevent potential audio cracking when the system is over
commissioned.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
The option --full-user is provided to delegate *all* scheduling
decisions to the user-space scheduler with no exception, including the
idle selection logic.
Therefore, make this option incompatible with --builtin-idle and
completely bypass the built-in idle selection logic when running in
full-user mode.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Provide a knob in scx_rustland_core to automatically turn the scheduler
into a simple FIFO when the system is underutilized.
This choice is based on the assumption that, in the case of system
underutilization (less tasks running than the amount of available CPUs),
the best scheduling policy is FIFO.
With this option enabled the scheduler starts in FIFO mode. If most of
the CPUs are busy (nr_running >= num_cpus - 1), the scheduler
immediately exits from FIFO mode and starts to apply the logic
implemented by the user-space component. Then the scheduler can switch
back to FIFO if there are no tasks waiting to be scheduled (evaluated
using a moving average).
This option can be enabled/disabled by the user-space scheduler using
the fifo_sched parameter in BpfScheduler: if set, the BPF component will
periodically check for system utilization and switch back and forth to
FIFO mode based on that.
This allows to improve performance of workloads that are using a small
amount of the available CPUs in the system, while still maintaining the
same good level of performance for interactive tasks when the system is
over commissioned.
In certain video games, such as Baldur's Gate 3 or Counter-Strike 2,
running in "normal" system conditions, we can experience a boost in fps
of approximately 4-8% with this change applied.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Simplify the CPU idle selection logic relying on the built-in logic.
If something can be improved in this logic it should be done in the
backend, changing the default idle selection logic, rustland doesn't
need to do anything special here for now.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
This merge included additional commits that were supposed to be included
in a separate pull request and have nothing to do with the fifo-mode
changes.
Therefore, revert the whole pull request and create a separate one with
the correct list of commits required to implement this feature.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Dispatch non-interactive tasks on the CPU selected by the built-in idle
selection logic and allow interactive tasks to be dispatched on any CPU.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
The shared DSQ is typically used to prioritize tasks and dispatch them
on the first CPU available, so consume from the shared DSQ before the
local CPU DSQ.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Do not always assign the maximum time slice to interactive tasks, but
use the same value of the dynamic time slice for everyone.
This seems to prevent potential audio cracking when the system is over
commissioned.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Provide a knob in scx_rustland_core to automatically turn the scheduler
into a simple FIFO when the system is underutilized.
This choice is based on the assumption that, in the case of system
underutilization (less tasks running than the amount of available CPUs),
the best scheduling policy is FIFO.
With this option enabled the scheduler starts in FIFO mode. If most of
the CPUs are busy (nr_running >= num_cpus - 1), the scheduler
immediately exits from FIFO mode and starts to apply the logic
implemented by the user-space component. Then the scheduler can switch
back to FIFO if there are no tasks waiting to be scheduled (evaluated
using a moving average).
This option can be enabled/disabled by the user-space scheduler using
the fifo_sched parameter in BpfScheduler: if set, the BPF component will
periodically check for system utilization and switch back and forth to
FIFO mode based on that.
This allows to improve performance of workloads that are using a small
amount of the available CPUs in the system, while still maintaining the
same good level of performance for interactive tasks when the system is
over commissioned.
In certain video games, such as Baldur's Gate 3 or Counter-Strike 2,
running in "normal" system conditions, we can experience a boost in fps
of approximately 4-8% with this change applied.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Simplify the CPU idle selection logic relying on the built-in logic.
If something can be improved in this logic it should be done in the
backend, changing the default idle selection logic, rustland doesn't
need to do anything special here for now.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
scx_simple is a basic scheduler that does either basic vtime, or global
FIFO, scheduling. At first glance, it may be confusing why we create a
separate DSQ rather than just using SCX_DSQ_GLOBAL. Let's add a comment
explaining the reason for this, so that users that are going over
scx_simple as an example scheduler don't get confused.
Signed-off-by: David Vernet <void@manifault.com>
It seems that libbpf and bpftool have some places where -Werror triggers
when compiled with gcc. Let's make it non-default. Users can always
enable it locally if they want to by invoking `meson setup` with the
--werror flag.
Signed-off-by: David Vernet <void@manifault.com>
Fix error:
INFO: autodetecting backend as ninja
INFO: calculating backend command to run: /usr/bin/ninja -C /home/lucjan/Pobrane/scx-scheds-git/src/scx/build
ninja: Entering directory `/home/lucjan/Pobrane/scx-scheds-git/src/scx/build'
[2/31] Generating bpftool_target with a custom command
FAILED: bpftool_dummy.c.__PHONY__
/bin/bash /home/lucjan/Pobrane/scx-scheds-git/src/scx/meson-scripts/build_bpftool /usr/bin/jq /usr/bin/make /home/lucjan/Pobrane/scx-scheds-git/src/scx/build/bpftool/src 4
libbpf.c: In function ‘bpf_object__gen_loader’:
libbpf.c: In function ‘bpf_object__gen_loader’:
libbpf.c:8994:28: error: ‘calloc’ sizes specified with ‘sizeof’ in the earlier argument and not in the later argument [-Werror=calloc-transposed-args]
8994 | gen = calloc(sizeof(*gen), 1);
| ^
libbpf.c:8994:28: error: ‘calloc’ sizes specified with ‘sizeof’ in the earlier argument and not in the later argument [-Werror=calloc-transposed-args]
8994 | gen = calloc(sizeof(*gen), 1);
| ^
libbpf.c:8994:28: note: earlier argument should specify number of elements, later size of each element
libbpf.c:8994:28: note: earlier argument should specify number of elements, later size of each element
At top level:
cc1: note: unrecognized command-line option ‘-Wno-unknown-warning-option’ may have been intended to silence earlier diagnostics
cc1: all warnings being treated as errors
make[1]: *** [Makefile:134: /home/lucjan/Pobrane/scx-scheds-git/src/scx/build/bpftool/src/bootstrap/libbpf/staticobjs/libbpf.o] Error 1
make: *** [Makefile:52: /home/lucjan/Pobrane/scx-scheds-git/src/scx/build/bpftool/src/bootstrap/libbpf/libbpf.a] Error 2
make: *** Waiting for unfinished jobs....
At top level:
cc1: note: unrecognized command-line option ‘-Wno-unknown-warning-option’ may have been intended to silence earlier diagnostics
cc1: all warnings being treated as errors
make[1]: *** [Makefile:134: /home/lucjan/Pobrane/scx-scheds-git/src/scx/build/bpftool/src/libbpf/staticobjs/libbpf.o] Error 1
make: *** [Makefile:44: /home/lucjan/Pobrane/scx-scheds-git/src/scx/build/bpftool/src/libbpf/libbpf.a] Error 2
ninja: build stopped: subcommand failed.
Signed-off-by: Piotr Gorski <lucjan.lucjanov@gmail.com>
Report the amount of running tasks to stdout. This value also represents
the amount of active CPUs that are currently executing a task.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Although newer kernels default to switching-all, some users might still
be using the scheduler with older kernels.
Therefore, ensure all tasks are moved to the SCHED_EXT class by calling
__COMPAT_scx_bpf_switch_all() during init, so that scx_simple can still
operate on these older kernels as well.
Fixes: cf66e58 ("Sync from kernel (670bdab6073)")
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Add '-Wno-maybe-uninitialized' option since gcc spits a warning (as an
error) at release build. Following is the error message without the
option.
❯ meson setup build -Dbuildtype=release --prefix ~
❯ meson compile -C build --jobs=$(nproc)
INFO: autodetecting backend as ninja
INFO: calculating backend command to run: /usr/bin/ninja -C /home/changwoo/ws-multics69/dev/scx-github/build -j 16
ninja: Entering directory `/home/changwoo/ws-multics69/dev/scx-github/build'
[3/40] Generating libbpf with a custom command
FAILED: cc_cflags_probe.c.__PHONY__
/home/changwoo/ws-multics69/dev/scx-github/meson-scripts/build_libbpf /usr/bin/jq /usr/bin/make /home/changwoo/ws-multics69/dev/scx-github/build/libbpf/src 16
In function ‘elf_close’,
inlined from ‘elf_close’ at elf.c:53:6,
inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2:
elf.c:57:9: error: ‘elf_fd.elf’ may be used uninitialized [-Werror=maybe-uninitialized]
57 | elf_end(elf_fd->elf);
| ^~~~~~~~~~~~~~~~~~~~
elf.c: In function ‘elf_find_func_offset_from_file’:
elf.c:377:23: note: ‘elf_fd.elf’ was declared here
377 | struct elf_fd elf_fd;
| ^~~~~~
In function ‘elf_close’,
inlined from ‘elf_close’ at elf.c:53:6,
inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2:
elf.c:58:9: error: ‘elf_fd.fd’ may be used uninitialized [-Werror=maybe-uninitialized]
58 | close(elf_fd->fd);
| ^~~~~~~~~~~~~~~~~
elf.c: In function ‘elf_find_func_offset_from_file’:
elf.c:377:23: note: ‘elf_fd.fd’ was declared here
377 | struct elf_fd elf_fd;
| ^~~~~~
At top level:
cc1: note: unrecognized command-line option ‘-Wno-unknown-warning-option’ may have been intended to silence earlier diagnostics
cc1: all warnings being treated as errors
make: *** [Makefile:133: staticobjs/elf.o] Error 1
make: *** Waiting for unfinished jobs....
libbpf.c: In function ‘bpf_map__init_kern_struct_ops’:
libbpf.c:1107:18: error: ‘mod_btf’ may be used uninitialized [-Werror=maybe-uninitialized]
1107 | kern_btf = mod_btf ? mod_btf->btf : obj->btf_vmlinux;
| ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
libbpf.c:1092:28: note: ‘mod_btf’ was declared here
1092 | struct module_btf *mod_btf;
| ^~~~~~~
In function ‘find_struct_ops_kern_types’,
inlined from ‘bpf_map__init_kern_struct_ops’ at libbpf.c:1100:8:
libbpf.c:980:21: error: ‘btf’ may be used uninitialized [-Werror=maybe-uninitialized]
980 | kern_type = btf__type_by_id(btf, kern_type_id);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
libbpf.c: In function ‘bpf_map__init_kern_struct_ops’:
libbpf.c:965:21: note: ‘btf’ was declared here
965 | struct btf *btf;
| ^~~
At top level:
cc1: note: unrecognized command-line option ‘-Wno-unknown-warning-option’ may have been intended to silence earlier diagnostics
cc1: all warnings being treated as errors
make: *** [Makefile:133: staticobjs/libbpf.o] Error 1
[4/40] Generating bpftool_target with a custom command
ninja: build stopped: subcommand failed.
Signed-off-by: Changwoo Min <changwoo@igalia.com>
The dynamic slice boost is not used anymore in the code, so there is no
reason to keep evaluating it.
Moreover, using it instead of the static slice boost seems to make
things worse, so let's just get rid of it.
Fixes: 0b3c399 ("scx_rustland: introduce dynamic slice boost")
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
scx_rustland has a function called get_cpu_owner() in BPF which
currently has no callers. There's nothing wrong with the function, but
it causes a warning due to an unused function. Let's just annotate it
with __maybe_unused to tell the compiler that it's not a problem.
Signed-off-by: David Vernet <void@manifault.com>
When building with warnings enabled, a few obvious bugs are pointed out:
- We're not correctly calculating waker frequency
- We're not taking the min of avg_run_raw compared to max latency
- We're missing an element from sched_prio_to_weight
Fix these. With these changes, interactivity is seemingly improved. We
go from ~12 sec / turn -> 11 seconds / turn in the Civ 6 AI benchmark
with a 4 x nproc CPU hogging workload in the background. It's clear,
however, that we really need preemption.
Signed-off-by: David Vernet <void@manifault.com>
meson has a builtin -werror option that can be passed to meson setup. So
as to allow users to specify if they want to treat warnings as errors,
let's add this flag to meson.build.
We elect to make the flag the default behavior for now, as warnings in
BPF scheds are not surfaced unless there is an actual compiler error.
The warning can be turned off by specifying `-D werror=false` when
invoking `meson setup`.
Signed-off-by: David Vernet <void@manifault.com>
C SCX_OPS_ATTACH() and rust scx_ops_attach() macros were not calling
.attach() and were only attaching the struct_ops. This meant that all
non-struct_ops BPF programs contained in the skels were never attached which
breaks e.g. scx_layered.
Let's fix it by adding .attach() invocation the the attach macros.
