os_illumos.go

Documentation: runtime

     1  // Copyright 2019 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package runtime
     6  
     7  import (
     8  	"unsafe"
     9  )
    10  
    11  //go:cgo_import_dynamic libc_getrctl getrctl "libc.so"
    12  //go:cgo_import_dynamic libc_rctlblk_get_local_action rctlblk_get_local_action "libc.so"
    13  //go:cgo_import_dynamic libc_rctlblk_get_local_flags rctlblk_get_local_flags "libc.so"
    14  //go:cgo_import_dynamic libc_rctlblk_get_value rctlblk_get_value "libc.so"
    15  //go:cgo_import_dynamic libc_rctlblk_size rctlblk_size "libc.so"
    16  
    17  //go:linkname libc_getrctl libc_getrctl
    18  //go:linkname libc_rctlblk_get_local_action libc_rctlblk_get_local_action
    19  //go:linkname libc_rctlblk_get_local_flags libc_rctlblk_get_local_flags
    20  //go:linkname libc_rctlblk_get_value libc_rctlblk_get_value
    21  //go:linkname libc_rctlblk_size libc_rctlblk_size
    22  
    23  var (
    24  	libc_getrctl,
    25  	libc_rctlblk_get_local_action,
    26  	libc_rctlblk_get_local_flags,
    27  	libc_rctlblk_get_value,
    28  	libc_rctlblk_size libcFunc
    29  )
    30  
    31  // Return the minimum value seen for the zone CPU cap, or 0 if no cap is
    32  // detected.
    33  func getcpucap() uint64 {
    34  	// The resource control block is an opaque object whose size is only
    35  	// known to libc.  In practice, given the contents, it is unlikely to
    36  	// grow beyond 8KB so we'll use a static buffer of that size here.
    37  	const rblkmaxsize = 8 * 1024
    38  	if rctlblk_size() > rblkmaxsize {
    39  		return 0
    40  	}
    41  
    42  	// The "zone.cpu-cap" resource control, as described in
    43  	// resource_controls(5), "sets a limit on the amount of CPU time that
    44  	// can be used by a zone.  The unit used is the percentage of a single
    45  	// CPU that can be used by all user threads in a zone, expressed as an
    46  	// integer."  A C string of the name must be passed to getrctl(2).
    47  	name := []byte("zone.cpu-cap\x00")
    48  
    49  	// To iterate over the list of values for a particular resource
    50  	// control, we need two blocks: one for the previously read value and
    51  	// one for the next value.
    52  	var rblk0 [rblkmaxsize]byte
    53  	var rblk1 [rblkmaxsize]byte
    54  	rblk := &rblk0[0]
    55  	rblkprev := &rblk1[0]
    56  
    57  	var flag uint32 = _RCTL_FIRST
    58  	var capval uint64 = 0
    59  
    60  	for {
    61  		if getrctl(unsafe.Pointer(&name[0]), unsafe.Pointer(rblkprev), unsafe.Pointer(rblk), flag) != 0 {
    62  			// The end of the sequence is reported as an ENOENT
    63  			// failure, but determining the CPU cap is not critical
    64  			// here.  We'll treat any failure as if it were the end
    65  			// of sequence.
    66  			break
    67  		}
    68  
    69  		lflags := rctlblk_get_local_flags(unsafe.Pointer(rblk))
    70  		action := rctlblk_get_local_action(unsafe.Pointer(rblk))
    71  		if (lflags&_RCTL_LOCAL_MAXIMAL) == 0 && action == _RCTL_LOCAL_DENY {
    72  			// This is a finite (not maximal) value representing a
    73  			// cap (deny) action.
    74  			v := rctlblk_get_value(unsafe.Pointer(rblk))
    75  			if capval == 0 || capval > v {
    76  				capval = v
    77  			}
    78  		}
    79  
    80  		// Swap the blocks around so that we can fetch the next value
    81  		t := rblk
    82  		rblk = rblkprev
    83  		rblkprev = t
    84  		flag = _RCTL_NEXT
    85  	}
    86  
    87  	return capval
    88  }
    89  
    90  func getncpu() int32 {
    91  	n := int32(sysconf(__SC_NPROCESSORS_ONLN))
    92  	if n < 1 {
    93  		return 1
    94  	}
    95  
    96  	if cents := int32(getcpucap()); cents > 0 {
    97  		// Convert from a percentage of CPUs to a number of CPUs,
    98  		// rounding up to make use of a fractional CPU
    99  		// e.g., 336% becomes 4 CPUs
   100  		ncap := (cents + 99) / 100
   101  		if ncap < n {
   102  			return ncap
   103  		}
   104  	}
   105  
   106  	return n
   107  }
   108  
   109  //go:nosplit
   110  func getrctl(controlname, oldbuf, newbuf unsafe.Pointer, flags uint32) uintptr {
   111  	return sysvicall4(&libc_getrctl, uintptr(controlname), uintptr(oldbuf), uintptr(newbuf), uintptr(flags))
   112  }
   113  
   114  //go:nosplit
   115  func rctlblk_get_local_action(buf unsafe.Pointer) uintptr {
   116  	return sysvicall2(&libc_rctlblk_get_local_action, uintptr(buf), uintptr(0))
   117  }
   118  
   119  //go:nosplit
   120  func rctlblk_get_local_flags(buf unsafe.Pointer) uintptr {
   121  	return sysvicall1(&libc_rctlblk_get_local_flags, uintptr(buf))
   122  }
   123  
   124  //go:nosplit
   125  func rctlblk_get_value(buf unsafe.Pointer) uint64 {
   126  	return uint64(sysvicall1(&libc_rctlblk_get_value, uintptr(buf)))
   127  }
   128  
   129  //go:nosplit
   130  func rctlblk_size() uintptr {
   131  	return sysvicall0(&libc_rctlblk_size)
   132  }
   133
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