nimbus-eth2/nbench/platforms/x86.nim

126 lines
4.1 KiB
Nim

# beacon_chain
# Copyright (c) 2018 Status Research & Development GmbH
# Licensed and distributed under either of
# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
# at your option. This file may not be copied, modified, or distributed except according to those terms.
# Cpu Name
# -------------------------------------------------------
{.passC:"-std=gnu99".} # TODO may conflict with milagro "-std=c99"
proc cpuID(eaxi, ecxi: int32): tuple[eax, ebx, ecx, edx: int32] =
when defined(vcc):
proc cpuidVcc(cpuInfo: ptr int32; functionID: int32)
{.importc: "__cpuidex", header: "intrin.h".}
cpuidVcc(addr result.eax, eaxi, ecxi)
else:
var (eaxr, ebxr, ecxr, edxr) = (0'i32, 0'i32, 0'i32, 0'i32)
asm """
cpuid
:"=a"(`eaxr`), "=b"(`ebxr`), "=c"(`ecxr`), "=d"(`edxr`)
:"a"(`eaxi`), "c"(`ecxi`)"""
(eaxr, ebxr, ecxr, edxr)
proc cpuName*(): string =
var leaves {.global.} = cast[array[48, char]]([
cpuID(eaxi = 0x80000002'i32, ecxi = 0),
cpuID(eaxi = 0x80000003'i32, ecxi = 0),
cpuID(eaxi = 0x80000004'i32, ecxi = 0)])
result = $cast[cstring](addr leaves[0])
# Counting cycles
# -------------------------------------------------------
# From Linux
#
# The RDTSC instruction is not ordered relative to memory
# access. The Intel SDM and the AMD APM are both vague on this
# point, but empirically an RDTSC instruction can be
# speculatively executed before prior loads. An RDTSC
# immediately after an appropriate barrier appears to be
# ordered as a normal load, that is, it provides the same
# ordering guarantees as reading from a global memory location
# that some other imaginary CPU is updating continuously with a
# time stamp.
#
# From Intel SDM
# https://www.intel.com/content/dam/www/public/us/en/documents/white-papers/ia-32-ia-64-benchmark-code-execution-paper.pdf
proc getTicks*(): int64 {.inline.} =
when defined(vcc):
proc rdtsc(): int64 {.sideeffect, importc: "__rdtsc", header: "<intrin.h>".}
proc lfence() {.importc: "__mm_lfence", header: "<intrin.h>".}
lfence()
return rdtsc()
else:
when defined(amd64):
var lo, hi: int64
# TODO: Provide a compile-time flag for RDTSCP support
# and use it instead of lfence + RDTSC
{.emit: """asm volatile(
"lfence\n"
"rdtsc\n"
: "=a"(`lo`), "=d"(`hi`)
:
: "memory"
);""".}
return (hi shl 32) or lo
else: # 32-bit x86
# TODO: Provide a compile-time flag for RDTSCP support
# and use it instead of lfence + RDTSC
{.emit: """asm volatile(
"lfence\n"
"rdtsc\n"
: "=a"(`result`)
:
: "memory"
);""".}
# Sanity check
# -------------------------------------------------------
when isMainModule:
import std/[times, monotimes, math, volatile, os]
block: # CpuName
echo "Your CPU is: "
echo " ", cpuName()
block: # Cycle Count
echo "The cost of an int64 modulo operation on your platform is:"
# Dealing with compiler optimization on microbenchmarks is hard
{.pragma: volatile, codegenDecl: "volatile $# $#".}
proc modNtimes(a, b: int64, N: int) {.noinline.} =
var c{.volatile.}: int64
for i in 0 ..< N:
c.addr.volatileStore(a.unsafeAddr.volatileLoad() mod b.unsafeAddr.volatileLoad())
let a {.volatile.} = 1000003'i64 # a prime number
let b {.volatile.} = 10007'i64 # another prime number
let N {.volatile.} = 3_000_000
let startMono = getMonoTime()
let startCycles = getTicks()
modNtimes(a, b, N)
let stopCycles = getTicks()
let stopMono = getMonoTime()
let elapsedMono = inNanoseconds(stopMono - startMono)
let elapsedCycles = stopCycles - startCycles
let timerResolutionGHz = round(elapsedCycles.float32 / elapsedMono.float32, 3)
echo " ", (elapsedCycles) div N, " cycles"
echo " ", (elapsedMono) div N, " ns/iter"
echo " ", timerResolutionGHz, " GHz (timer resolution)"
block: # CPU Frequency
discard # TODO, surprisingly this is very complex