1.\" Copyright (c) 2008 Yahoo!, Inc. 2.\" All rights reserved. 3.\" Written by: John Baldwin <jhb@FreeBSD.org> 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 3. Neither the name of the author nor the names of any co-contributors 14.\" may be used to endorse or promote products derived from this software 15.\" without specific prior written permission. 16.\" 17.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27.\" SUCH DAMAGE. 28.\" 29.Dd March 15, 2017 30.Dt KVM_GETPCPU 3 31.Os 32.Sh NAME 33.Nm kvm_dpcpu_setcpu , 34.Nm kvm_getmaxcpu , 35.Nm kvm_getpcpu 36.Nd access per-CPU data 37.Sh LIBRARY 38.Lb libkvm 39.Sh SYNOPSIS 40.In sys/param.h 41.In sys/pcpu.h 42.In sys/sysctl.h 43.In kvm.h 44.Ft int 45.Fn kvm_dpcpu_setcpu "kvm_t *kd" "u_int cpu" 46.Ft int 47.Fn kvm_getmaxcpu "kvm_t *kd" 48.Ft int 49.Fn kvm_getncpus "kvm_t *kd" 50.Ft void * 51.Fn kvm_getpcpu "kvm_t *kd" "int cpu" 52.Ft ssize_t 53.Fn kvm_read_zpcpu "kvm_t *kd" "u_long base" "void *buf" "size_t size" "int cpu" 54.Ft uint64_t 55.Fn kvm_counter_u64_fetch "kvm_t *kd" "u_long base" 56.Sh DESCRIPTION 57The 58.Fn kvm_dpcpu_setcpu , 59.Fn kvm_getmaxcpu , 60and 61.Fn kvm_getpcpu 62functions are used to access the per-CPU data of active processors in the 63kernel indicated by 64.Fa kd . 65Per-CPU storage comes in two flavours: data stored directly in a 66.Vt "struct pcpu" 67associated with each CPU, and dynamic per-CPU storage (DPCPU), in which a 68single kernel symbol refers to different data depending on what CPU it is 69accessed from. 70.Pp 71The 72.Fn kvm_getmaxcpu 73function returns the maximum number of CPUs supported by the kernel. 74.Pp 75The 76.Fn kvm_getncpus 77function returns the current number of CPUs in the kernel. 78.Pp 79The 80.Fn kvm_getpcpu 81function returns a buffer holding the per-CPU data for a single CPU. 82This buffer is described by the 83.Vt "struct pcpu" 84type. 85The caller is responsible for releasing the buffer via a call to 86.Xr free 3 87when it is no longer needed. 88If 89.Fa cpu 90is not active, then 91.Dv NULL 92is returned instead. 93.Pp 94The 95.Fn kvm_read_zpcpu 96function is used to obtain private per-CPU copy from a 97.Dv UMA_ZONE_PCPU 98.Xr zone 9 . 99It takes 100.Fa base 101argument as base address of an allocation and copyies 102.Fa size 103bytes into 104.Fa buf 105from the part of allocation that is private to 106.Fa cpu . 107.Pp 108The 109.Fn kvm_counter_u64_fetch 110function fetches value of a 111.Xr counter 9 112pointed by 113.Fa base 114address. 115.Pp 116Symbols for dynamic per-CPU data are accessed via 117.Xr kvm_nlist 3 118as with other symbols. 119.Nm libkvm 120maintains a notion of the "current CPU", set by 121.Fn kvm_dpcpu_setcpu , 122which defaults to 0. 123Once another CPU is selected, 124.Xr kvm_nlist 3 125will return pointers to that data on the appropriate CPU. 126.Sh CACHING 127.Fn kvm_getmaxcpu 128and 129.Fn kvm_getpcpu 130cache the nlist values for various kernel variables which are 131reused in successive calls. 132You may call either function with 133.Fa kd 134set to 135.Dv NULL 136to clear this cache. 137.Sh RETURN VALUES 138On success, the 139.Fn kvm_getmaxcpu 140function returns the maximum number of CPUs supported by the kernel. 141If an error occurs, 142it returns -1 instead. 143.Pp 144On success, the 145.Fn kvm_getpcpu 146function returns a pointer to an allocated buffer or 147.Dv NULL . 148If an error occurs, 149it returns -1 instead. 150.Pp 151On success, the 152.Fn kvm_dpcpu_setcpu 153call returns 0; if an error occurs, it returns -1 instead. 154.Pp 155On success, the 156.Fn kvm_read_zpcpu 157function returns number of bytes copied. 158If an error occurs, it returns -1 instead. 159.Pp 160If any function encounters an error, 161then an error message may be retrieved via 162.Xr kvm_geterr 3 . 163.Sh SEE ALSO 164.Xr free 3 , 165.Xr kvm 3 , 166.Xr counter 9 , 167.Xr zone 9 168