forked from lix-project/lix
Run the daemon worker on the same CPU as the client
On a system with multiple CPUs, running Nix operations through the daemon is significantly slower than "direct" mode: $ NIX_REMOTE= nix-instantiate '<nixos>' -A system real 0m0.974s user 0m0.875s sys 0m0.088s $ NIX_REMOTE=daemon nix-instantiate '<nixos>' -A system real 0m2.118s user 0m1.463s sys 0m0.218s The main reason seems to be that the client and the worker get moved to a different CPU after every call to the worker. This patch adds a hack to lock them to the same CPU. With this, the overhead of going through the daemon is very small: $ NIX_REMOTE=daemon nix-instantiate '<nixos>' -A system real 0m1.074s user 0m0.809s sys 0m0.098s
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263d668222
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@ -127,6 +127,10 @@ AC_CHECK_HEADERS([sys/mount.h], [], [],
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AC_CHECK_FUNCS([lutimes])
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# Check for sched_setaffinity.
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AC_CHECK_FUNCS([sched_setaffinity])
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# Check whether the store optimiser can optimise symlinks.
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AC_MSG_CHECKING([whether it is possible to create a link to a symlink])
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ln -s bla tmp_link
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@ -7,6 +7,7 @@
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#include "local-store.hh"
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#include "util.hh"
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#include "archive.hh"
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#include "affinity.hh"
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#include <map>
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#include <sstream>
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@ -366,6 +367,8 @@ void Goal::trace(const format & f)
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/* Common initialisation performed in child processes. */
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static void commonChildInit(Pipe & logPipe)
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{
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restoreAffinity();
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/* Put the child in a separate session (and thus a separate
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process group) so that it has no controlling terminal (meaning
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that e.g. ssh cannot open /dev/tty) and it doesn't receive
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@ -568,6 +571,7 @@ static void runSetuidHelper(const string & command,
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args.push_back(0);
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restoreSIGPIPE();
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restoreAffinity();
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execve(program.c_str(), (char * *) &args[0], 0);
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throw SysError(format("executing `%1%'") % program);
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@ -5,6 +5,7 @@
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#include "pathlocks.hh"
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#include "worker-protocol.hh"
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#include "derivations.hh"
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#include "affinity.hh"
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#include <iostream>
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#include <algorithm>
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@ -1021,6 +1022,7 @@ void LocalStore::startSubstituter(const Path & substituter, RunningSubstituter &
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case 0: /* child */
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try {
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restoreAffinity();
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if (dup2(toPipe.readSide, STDIN_FILENO) == -1)
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throw SysError("dupping stdin");
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if (dup2(fromPipe.writeSide, STDOUT_FILENO) == -1)
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@ -3,6 +3,7 @@
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#include "remote-store.hh"
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#include "worker-protocol.hh"
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#include "archive.hh"
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#include "affinity.hh"
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#include "globals.hh"
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#include <sys/types.h>
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@ -15,7 +16,6 @@
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#include <unistd.h>
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#include <cstring>
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namespace nix {
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@ -71,8 +71,19 @@ void RemoteStore::openConnection(bool reserveSpace)
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if (GET_PROTOCOL_MAJOR(daemonVersion) != GET_PROTOCOL_MAJOR(PROTOCOL_VERSION))
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throw Error("Nix daemon protocol version not supported");
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writeInt(PROTOCOL_VERSION, to);
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if (GET_PROTOCOL_MINOR(daemonVersion) >= 14) {
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int cpu = lockToCurrentCPU();
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if (cpu != -1) {
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writeInt(1, to);
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writeInt(cpu, to);
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} else
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writeInt(0, to);
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}
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if (GET_PROTOCOL_MINOR(daemonVersion) >= 11)
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writeInt(reserveSpace, to);
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processStderr();
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}
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catch (Error & e) {
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@ -6,7 +6,7 @@ namespace nix {
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#define WORKER_MAGIC_1 0x6e697863
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#define WORKER_MAGIC_2 0x6478696f
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#define PROTOCOL_VERSION 0x10d
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#define PROTOCOL_VERSION 0x10e
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#define GET_PROTOCOL_MAJOR(x) ((x) & 0xff00)
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#define GET_PROTOCOL_MINOR(x) ((x) & 0x00ff)
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@ -1,12 +1,12 @@
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pkglib_LTLIBRARIES = libutil.la
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libutil_la_SOURCES = util.cc hash.cc serialise.cc \
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archive.cc xml-writer.cc
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archive.cc xml-writer.cc affinity.cc
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libutil_la_LIBADD = ../boost/format/libformat.la
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pkginclude_HEADERS = util.hh hash.hh serialise.hh \
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archive.hh xml-writer.hh types.hh
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archive.hh xml-writer.hh types.hh affinity.hh
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if !HAVE_OPENSSL
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libutil_la_SOURCES += \
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54
src/libutil/affinity.cc
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54
src/libutil/affinity.cc
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@ -0,0 +1,54 @@
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#include "types.hh"
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#include "util.hh"
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#include "affinity.hh"
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#if HAVE_SCHED_H
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#include <sched.h>
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#endif
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namespace nix {
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static bool didSaveAffinity = false;
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static cpu_set_t savedAffinity;
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void setAffinityTo(int cpu)
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{
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#if HAVE_SCHED_SETAFFINITY
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if (sched_getaffinity(0, sizeof(cpu_set_t), &savedAffinity) == -1) return;
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didSaveAffinity = true;
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printMsg(lvlDebug, format("locking this thread to CPU %1%") % cpu);
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cpu_set_t newAffinity;
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CPU_ZERO(&newAffinity);
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CPU_SET(cpu, &newAffinity);
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if (sched_setaffinity(0, sizeof(cpu_set_t), &newAffinity) == -1)
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printMsg(lvlError, format("failed to lock thread to CPU %1%") % cpu);
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#endif
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}
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int lockToCurrentCPU()
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{
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#if HAVE_SCHED_SETAFFINITY
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if (getEnv("NIX_AFFINITY_HACK", "1") == "1") {
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int cpu = sched_getcpu();
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if (cpu != -1) setAffinityTo(cpu);
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return cpu;
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}
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#endif
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return -1;
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}
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void restoreAffinity()
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{
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#if HAVE_SCHED_SETAFFINITY
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if (!didSaveAffinity) return;
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if (sched_setaffinity(0, sizeof(cpu_set_t), &savedAffinity) == -1)
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printMsg(lvlError, "failed to restore affinity %1%");
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#endif
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}
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}
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9
src/libutil/affinity.hh
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9
src/libutil/affinity.hh
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@ -0,0 +1,9 @@
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#pragma once
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namespace nix {
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void setAffinityTo(int cpu);
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int lockToCurrentCPU();
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void restoreAffinity();
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}
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@ -4,6 +4,7 @@
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#include "serialise.hh"
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#include "worker-protocol.hh"
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#include "archive.hh"
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#include "affinity.hh"
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#include "globals.hh"
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#include <cstring>
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@ -671,6 +672,9 @@ static void processConnection(bool trusted)
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to.flush();
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unsigned int clientVersion = readInt(from);
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if (GET_PROTOCOL_MINOR(clientVersion) >= 14 && readInt(from))
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setAffinityTo(readInt(from));
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bool reserveSpace = true;
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if (GET_PROTOCOL_MINOR(clientVersion) >= 11)
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reserveSpace = readInt(from) != 0;
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