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Run the daemon worker on the same CPU as the client

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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
This commit is contained in:
Eelco Dolstra 2013-08-07 11:51:55 +00:00
parent 263d668222
commit a583a2bc59
9 changed files with 92 additions and 4 deletions
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2
src/libstore/local-store.cc
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@ -5,6 +5,7 @@
#include "pathlocks.hh"
#include "worker-protocol.hh"
#include "derivations.hh"
#include "affinity.hh"
#include <iostream>
#include <algorithm>
@ -1021,6 +1022,7 @@ void LocalStore::startSubstituter(const Path & substituter, RunningSubstituter &
case 0: /* child */
try {
restoreAffinity();
if (dup2(toPipe.readSide, STDIN_FILENO) == -1)
throw SysError("dupping stdin");
if (dup2(fromPipe.writeSide, STDOUT_FILENO) == -1)