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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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4
src/nix-daemon/nix-daemon.cc
View file

@ -4,6 +4,7 @@
#include "serialise.hh"
#include "worker-protocol.hh"
#include "archive.hh"
#include "affinity.hh"
#include "globals.hh"
#include <cstring>
@ -671,6 +672,9 @@ static void processConnection(bool trusted)
to.flush();
unsigned int clientVersion = readInt(from);
if (GET_PROTOCOL_MINOR(clientVersion) >= 14 && readInt(from))
setAffinityTo(readInt(from));
bool reserveSpace = true;
if (GET_PROTOCOL_MINOR(clientVersion) >= 11)
reserveSpace = readInt(from) != 0;