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04685e633f
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Andrea Righi 04685e633f scx_rustland: avoid memory copies while accessing cpu_map 
Instead of using a BPF_MAP_TYPE_ARRAY to store which tasks are running
on which CPU we can simply use a global array, mapped in the user-space
address space.

In this way we can avoid a lot of memory copies and call to sys_bpf(),
significantly reducing the scheduler's overhead.

Keep in mind that we don't need to be 100% correct while accessing this
information, so we can accept some fuzziness in order to significantly
reduce the scheduler's overhead.

Performance profile before this change:

   5.52%  [kernel]  [k] __sys_bpf
   4.84%  [kernel]  [k] __kmem_cache_alloc_node
   4.71%  [kernel]  [k] map_lookup_elem
   4.10%  [kernel]  [k] _copy_from_user
   3.51%  [kernel]  [k] bpf_map_copy_value
   3.12%  [kernel]  [k] check_heap_object

After this change:

   2.20%  [kernel]  [k] __sys_bpf
   1.91%  [kernel]  [k] map_lookup_and_delete_elem
   1.60%  [kernel]  [k] __kmem_cache_alloc_node
   1.10%  [kernel]  [k] _copy_from_user
   0.12%  [kernel]  [k] check_heap_object
                    n/a bpf_map_copy_value
                    n/a map_lookup_elem

With this change we can reduce the overhead of sys_bpf() by ~2x and
the overhead of copy_from_user() by ~4x.

Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
2024-02-20 12:30:16 +01:00
..
scx_layered scx_layered: Use scx_utils::user_exit_info 2024-01-31 10:54:20 -10:00
scx_rustland scx_rustland: avoid memory copies while accessing cpu_map 2024-02-20 12:30:16 +01:00
scx_rusty scx: Implement solution to infeasible weights problem 2024-02-09 16:23:12 -06:00
meson.build scx_rustland: rename from scx_rustlite 2023-12-22 00:20:14 +01:00
README.md Add README files for each rust scheduler 2024-01-04 07:35:44 -08:00

README.md

RUST SCHEDULERS

Introduction

This directory contains schedulers with user space rust components.

The README in each scheduler directory provides some background and describes the types of workloads or scenarios they're designed to accommodate. For more details on any of these schedulers, please see the header comment in their main.rs or *.bpf.c files.

Schedulers