Remove CPU locking

This was already accidentally disabled in ba87b08. It also no longer
appears to be beneficial, and in fact slow things down, e.g. when
evaluating a NixOS system configuration:

  elapsed time:       median =      3.8170  mean =      3.8202  stddev =      0.0195  min =      3.7894  max =      3.8600  [rejected, p=0.00000, Δ=0.36929±0.02513]
This commit is contained in:
Eelco Dolstra 2021-12-22 15:49:51 +01:00
parent ddd7839154
commit 9747ea84b4
11 changed files with 5 additions and 100 deletions

View file

@ -4,7 +4,6 @@
#include "store-api.hh"
#include "path-with-outputs.hh"
#include "finally.hh"
#include "affinity.hh"
#include "archive.hh"
#include "derivations.hh"
#include "args.hh"
@ -960,8 +959,8 @@ void processConnection(
});
if (GET_PROTOCOL_MINOR(clientVersion) >= 14 && readInt(from)) {
auto affinity = readInt(from);
setAffinityTo(affinity);
// Obsolete CPU affinity.
readInt(from);
}
readInt(from); // obsolete reserveSpace

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@ -5,7 +5,6 @@
#include "remote-store.hh"
#include "worker-protocol.hh"
#include "archive.hh"
#include "affinity.hh"
#include "globals.hh"
#include "derivations.hh"
#include "pool.hh"
@ -184,11 +183,8 @@ void RemoteStore::initConnection(Connection & conn)
conn.to << PROTOCOL_VERSION;
if (GET_PROTOCOL_MINOR(conn.daemonVersion) >= 14) {
int cpu = sameMachine() && settings.lockCPU ? lockToCurrentCPU() : -1;
if (cpu != -1)
conn.to << 1 << cpu;
else
conn.to << 0;
// Obsolete CPU affinity.
conn.to << 0;
}
if (GET_PROTOCOL_MINOR(conn.daemonVersion) >= 11)

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@ -1,70 +0,0 @@
#include "types.hh"
#include "util.hh"
#include "affinity.hh"
#if __linux__
#include <sched.h>
#endif
namespace nix {
#if __linux__
static bool didSaveAffinity = false;
static cpu_set_t savedAffinity;
std::ostream& operator<<(std::ostream &os, const cpu_set_t &cset)
{
auto count = CPU_COUNT(&cset);
for (int i=0; i < count; ++i)
{
os << (CPU_ISSET(i,&cset) ? "1" : "0");
}
return os;
}
#endif
void setAffinityTo(int cpu)
{
#if __linux__
if (sched_getaffinity(0, sizeof(cpu_set_t), &savedAffinity) == -1) return;
didSaveAffinity = true;
debug(format("locking this thread to CPU %1%") % cpu);
cpu_set_t newAffinity;
CPU_ZERO(&newAffinity);
CPU_SET(cpu, &newAffinity);
if (sched_setaffinity(0, sizeof(cpu_set_t), &newAffinity) == -1)
printError("failed to lock thread to CPU %1%", cpu);
#endif
}
int lockToCurrentCPU()
{
#if __linux__
int cpu = sched_getcpu();
if (cpu != -1) setAffinityTo(cpu);
return cpu;
#else
return -1;
#endif
}
void restoreAffinity()
{
#if __linux__
if (!didSaveAffinity) return;
if (sched_setaffinity(0, sizeof(cpu_set_t), &savedAffinity) == -1)
{
std::ostringstream oss;
oss << savedAffinity;
printError("failed to restore CPU affinity %1%", oss.str());
}
#endif
}
}

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@ -1,9 +0,0 @@
#pragma once
namespace nix {
void setAffinityTo(int cpu);
int lockToCurrentCPU();
void restoreAffinity();
}

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@ -1,13 +1,10 @@
#include "thread-pool.hh"
#include "affinity.hh"
namespace nix {
ThreadPool::ThreadPool(size_t _maxThreads)
: maxThreads(_maxThreads)
{
restoreAffinity(); // FIXME
if (!maxThreads) {
maxThreads = std::thread::hardware_concurrency();
if (!maxThreads) maxThreads = 1;

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@ -1,5 +1,4 @@
#include "util.hh"
#include "affinity.hh"
#include "sync.hh"
#include "finally.hh"
#include "serialise.hh"
@ -1004,7 +1003,6 @@ pid_t startProcess(std::function<void()> fun, const ProcessOptions & options)
if (options.dieWithParent && prctl(PR_SET_PDEATHSIG, SIGKILL) == -1)
throw SysError("setting death signal");
#endif
restoreAffinity();
fun();
} catch (std::exception & e) {
try {
@ -1675,8 +1673,6 @@ void restoreProcessContext(bool restoreMounts)
restoreMountNamespace();
}
restoreAffinity();
#if __linux__
if (savedStackSize) {
struct rlimit limit;

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@ -300,7 +300,7 @@ void setStackSize(size_t stackSize);
/* Restore the original inherited Unix process context (such as signal
masks, stack size, CPU affinity). */
masks, stack size). */
void restoreProcessContext(bool restoreMounts = true);
/* Save the current mount namespace. Ignored if called more than

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@ -14,7 +14,6 @@
#include "local-fs-store.hh"
#include "globals.hh"
#include "derivations.hh"
#include "affinity.hh"
#include "util.hh"
#include "shared.hh"
#include "path-with-outputs.hh"

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@ -5,7 +5,6 @@
#include "store-api.hh"
#include "path-with-outputs.hh"
#include "derivations.hh"
#include "affinity.hh"
#include "progress-bar.hh"
#include "run.hh"

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@ -28,7 +28,6 @@ extern "C" {
#include "common-eval-args.hh"
#include "get-drvs.hh"
#include "derivations.hh"
#include "affinity.hh"
#include "globals.hh"
#include "command.hh"
#include "finally.hh"

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@ -8,7 +8,6 @@
#include "finally.hh"
#include "fs-accessor.hh"
#include "progress-bar.hh"
#include "affinity.hh"
#include "eval.hh"
#if __linux__