| Message ID | 20230226162639.20559-2-ammarfaizi2@gnuweeb.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Documentation: Introducing `wq_cpu_set` mount option for btrfs | expand |
On Sun, Feb 26, 2023 at 11:26:38PM +0700, Ammar Faizi wrote: > +wq_cpu_set=<cpu_set> > + (since: 6.5, default: all online CPUs) Why will the knob be introduced in 6.5 instead? > + > + Btrfs workqueues can slow sensitive user tasks down because they can use any > + online CPU to perform heavy workloads on an SMP system. This option is used to > + isolate the Btrfs workqueues to a set of CPUs. It is helpful to avoid > + sensitive user tasks being preempted by Btrfs heavy workqueues. > + > + The *cpu_set* is a dot-separated list of decimal numbers and ranges. The > + numbers are CPU numbers, the ranges are inclusive. For example: "*cpu_set* is a dot-separated list of CPU numbers. Both individual number and range (inclusive) can be listed". > + > + - *wq_cpu_set=0.3-7* will use CPUs 0, 3, 4, 5, 6 and 7. > + > + - *wq_cpu_set=0.4.1.5* will use CPUs 0, 1, 4 and 5. > + > + This option is similar to the taskset bitmask except that the comma separator > + is replaced with a dot. The reason for this is that the mount option parser > + uses commas to separate mount options. "... replaced by dots, since commas has already been used as mount options separator". > + If *wq_cpu_set* option is specificed and the *thread_pool* option is also > + specified, the thread pool size will be set to the value of *thread_pool* > + option. "If both options are set ..." Thanks.
On Mon, Feb 27, 2023 at 09:24:16AM +0700, Bagas Sanjaya wrote: > "*cpu_set* is a dot-separated list of CPU numbers. Both individual > number and range (inclusive) can be listed". Folded in. > "... replaced by dots, since commas has already been used as mount > options separator". Folded in with s/commas/comma/. > "If both options are set ..." Folded in. Thanks,
diff --git a/Documentation/ch-mount-options.rst b/Documentation/ch-mount-options.rst index f0f205dc20fa15ff..48fe63ee5e95c297 100644 --- a/Documentation/ch-mount-options.rst +++ b/Documentation/ch-mount-options.rst @@ -451,6 +451,35 @@ user_subvol_rm_allowed ordinary directory. Whether this is possible can be detected at runtime, see *rmdir_subvol* feature in *FILESYSTEM FEATURES*. +wq_cpu_set=<cpu_set> + (since: 6.5, default: all online CPUs) + + Btrfs workqueues can slow sensitive user tasks down because they can use any + online CPU to perform heavy workloads on an SMP system. This option is used to + isolate the Btrfs workqueues to a set of CPUs. It is helpful to avoid + sensitive user tasks being preempted by Btrfs heavy workqueues. + + The *cpu_set* is a dot-separated list of decimal numbers and ranges. The + numbers are CPU numbers, the ranges are inclusive. For example: + + - *wq_cpu_set=0.3-7* will use CPUs 0, 3, 4, 5, 6 and 7. + + - *wq_cpu_set=0.4.1.5* will use CPUs 0, 1, 4 and 5. + + This option is similar to the taskset bitmask except that the comma separator + is replaced with a dot. The reason for this is that the mount option parser + uses commas to separate mount options. + + If *wq_cpu_set* option is specificed and the *thread_pool* option is not, the + number of default max thread pool size will be set to the number of online + CPUs in the specified CPU set plus 2, if and only if the resulting number is + less than 8. + + If *wq_cpu_set* option is specificed and the *thread_pool* option is also + specified, the thread pool size will be set to the value of *thread_pool* + option. + + DEPRECATED MOUNT OPTIONS ^^^^^^^^^^^^^^^^^^^^^^^^
Document a new Btrfs mount option, wq_cpu_set. Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org> --- Documentation/ch-mount-options.rst | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+)