doc: add Windows processor group behaviour and Windows target option

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index dbbbfaa1d839e2d0bd73d91ceb83956c69f8e2c2..e4d3198e49559e0e085cd04e8adc2fa8495a424e 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -2377,24 +2377,27 @@ Threads, processes and job synchronization
 
        Set the I/O priority class. See man :manpage:`ionice(1)`.
 
 
        Set the I/O priority class. See man :manpage:`ionice(1)`.
 

-.. option:: cpumask=int
-
-       Set the CPU affinity of this job. The parameter given is a bit mask of
-       allowed CPUs the job may run on. So if you want the allowed CPUs to be 1
-       and 5, you would pass the decimal value of (1 << 1 | 1 << 5), or 34. See man
-       :manpage:`sched_setaffinity(2)`. This may not work on all supported
-       operating systems or kernel versions. This option doesn't work well for a
-       higher CPU count than what you can store in an integer mask, so it can only
-       control cpus 1-32. For boxes with larger CPU counts, use
-       :option:`cpus_allowed`.
-

 .. option:: cpus_allowed=str
 
        Controls the same options as :option:`cpumask`, but accepts a textual
 .. option:: cpus_allowed=str
 
        Controls the same options as :option:`cpumask`, but accepts a textual

-       specification of the permitted CPUs instead. So to use CPUs 1 and 5 you
-       would specify ``cpus_allowed=1,5``. This option also allows a range of CPUs
-       to be specified -- say you wanted a binding to CPUs 1, 5, and 8 to 15, you
-       would set ``cpus_allowed=1,5,8-15``.
+       specification of the permitted CPUs instead and CPUs are indexed from 0. So
+       to use CPUs 0 and 5 you would specify ``cpus_allowed=0,5``. This option also
+       allows a range of CPUs to be specified -- say you wanted a binding to CPUs
+       0, 5, and 8 to 15, you would set ``cpus_allowed=0,5,8-15``.
+
+       On Windows, when ``cpus_allowed`` is unset only CPUs from fio's current
+       processor group will be used and affinity settings are inherited from the
+       system. An fio build configured to target Windows 7 makes options that set
+       CPUs processor group aware and values will set both the processor group
+       and a CPU from within that group. For example, on a system where processor
+       group 0 has 40 CPUs and processor group 1 has 32 CPUs, ``cpus_allowed``
+       values between 0 and 39 will bind CPUs from processor group 0 and
+       ``cpus_allowed`` values between 40 and 71 will bind CPUs from processor
+       group 1. When using ``cpus_allowed_policy=shared`` all CPUs specified by a
+       single ``cpus_allowed`` option must be from the same processor group. For
+       Windows fio builds not built for Windows 7, CPUs will only be selected from
+       (and be relative to) whatever processor group fio happens to be running in
+       and CPUs from other processor groups cannot be used.

 
 .. option:: cpus_allowed_policy=str
 
 
 .. option:: cpus_allowed_policy=str
 


@@ -2411,6 +2414,17 @@ Threads, processes and job synchronization
        enough CPUs are given for the jobs listed, then fio will roundrobin the CPUs
        in the set.
 
        enough CPUs are given for the jobs listed, then fio will roundrobin the CPUs
        in the set.
 

+.. option:: cpumask=int
+
+       Set the CPU affinity of this job. The parameter given is a bit mask of
+       allowed CPUs the job may run on. So if you want the allowed CPUs to be 1
+       and 5, you would pass the decimal value of (1 << 1 | 1 << 5), or 34. See man
+       :manpage:`sched_setaffinity(2)`. This may not work on all supported
+       operating systems or kernel versions. This option doesn't work well for a
+       higher CPU count than what you can store in an integer mask, so it can only
+       control cpus 1-32. For boxes with larger CPU counts, use
+       :option:`cpus_allowed`.
+

 .. option:: numa_cpu_nodes=str
 
        Set this job running on specified NUMA nodes' CPUs. The arguments allow
 .. option:: numa_cpu_nodes=str
 
        Set this job running on specified NUMA nodes' CPUs. The arguments allow