8d791e5af1
bus_get_cpus() returns a specified set of CPUs for a device. It accepts an enum for the second parameter that indicates the type of cpuset to request. Currently two valus are supported: - LOCAL_CPUS (on x86 this returns all the CPUs in the package closest to the device when DEVICE_NUMA is enabled) - INTR_CPUS (like LOCAL_CPUS but only returns 1 SMT thread for each core) For systems that do not support NUMA (or if it is not enabled in the kernel config), LOCAL_CPUS fails with EINVAL. INTR_CPUS is mapped to 'all_cpus' by default. The idea is that INTR_CPUS should always return a valid set. Device drivers which want to use per-CPU interrupts should start using INTR_CPUS instead of simply assigning interrupts to all available CPUs. In the future we may wish to add tunables to control the policy of INTR_CPUS (e.g. should it be local-only or global, should it ignore SMT threads or not). The x86 nexus driver exposes the internal set of interrupt CPUs from the the x86 interrupt code via INTR_CPUS. The ACPI bus driver and PCI bridge drivers use _PXM to return a suitable LOCAL_CPUS set when _PXM exists and DEVICE_NUMA is enabled. They also and the global INTR_CPUS set from the nexus driver with the per-domain set from _PXM to generate a local INTR_CPUS set for child devices. Compared to the r298933, this version uses 'struct _cpuset' in <sys/bus.h> instead of 'cpuset_t' to avoid requiring <sys/param.h> (<sys/_cpuset.h> still requires <sys/param.h> for MAXCPU even though <sys/_bitset.h> does not after recent changes).
102 lines
3.1 KiB
Groff
102 lines
3.1 KiB
Groff
.\" -*- nroff -*-
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.\"
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.\" Copyright (c) 2016 John H. Baldwin <jhb@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd March 1, 2016
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.Dt BUS_GET_CPUS 9
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.Os
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.Sh NAME
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.Nm BUS_GET_CPUS ,
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.Nm bus_get_cpus
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.Nd "request a set of device-specific CPUs"
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.Sh SYNOPSIS
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.In sys/param.h
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.In sys/bus.h
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.In sys/cpuset.h
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.Ft int
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.Fo BUS_GET_CPUS
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.Fa "device_t dev" "device_t child" "enum cpu_sets op" "size_t setsize"
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.Fa "cpuset_t *cpuset"
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.Fc
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.Ft int
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.Fo bus_get_cpus
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.Fa "device_t dev" "enum cpu_sets op" "size_t setsize" "cpuset_t *cpuset"
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.Fc
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.Sh DESCRIPTION
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The
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.Fn BUS_GET_CPUS
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method queries the parent bus device for a set of device-specific CPUs.
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The
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.Fa op
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argument specifies which set of CPUs to retrieve.
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If successful,
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the requested set of CPUs are returned in
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.Fa cpuset .
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The
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.Fa setsize
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argument specifies the size in bytes of the set passed in
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.Fa cpuset .
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.Pp
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.Fn BUS_GET_CPUS
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supports querying different types of CPU sets via the the
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.Fa op argument.
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Not all set types are supported for every device.
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If a set type is not supported,
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.Fn BUS_GET_CPUS
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fails with
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.Er EINVAL .
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These set types are supported:
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.Bl -tag -width ".Dv LOCAL_CPUS"
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.It Dv LOCAL_CPUS
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The set of CPUs that are local to the device.
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If a device is closer to a specific memory domain in a non-uniform memory
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architecture system
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.Pq NUMA ,
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this will return the set of CPUs in that memory domain.
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.It Dv INTR_CPUS
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The preferred set of CPUs that this device should use for device interrupts.
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This set type must be supported by all bus drivers.
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.El
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.Pp
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The
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.Fn bus_get_cpus
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function is a simple wrapper around
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.Fn BUS_GET_CPUS .
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.Sh RETURN VALUES
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Zero is returned on success, otherwise an appropriate error is returned.
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.Sh SEE ALSO
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.Xr cpuset 2 ,
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.Xr BUS_BIND_INTR 9 ,
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.Xr device 9
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.Sh HISTORY
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The
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.Fn BUS_GET_CPUS
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method and
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.Fn bus_get_cpus
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function first appeared in
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.Fx 11.0 .
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