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authorEelco Dolstra <eelco.dolstra@logicblox.com>2013-08-07T11·51+0000
committerEelco Dolstra <eelco.dolstra@logicblox.com>2013-08-07T12·02+0200
commita583a2bc59a4ee2b067e5520f6c5bc0c61852c32 (patch)
tree137be66f58b664dbf0aa21138000d711d5e00162 /src/libstore/remote-store.cc
parent263d6682224f516aed74286453c5e2e097a38aa6 (diff)
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
Diffstat (limited to 'src/libstore/remote-store.cc')
-rw-r--r--src/libstore/remote-store.cc13
1 files changed, 12 insertions, 1 deletions
diff --git a/src/libstore/remote-store.cc b/src/libstore/remote-store.cc
index 2b5a932131c3..3764b4813a4e 100644
--- a/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -3,6 +3,7 @@
 #include "remote-store.hh"
 #include "worker-protocol.hh"
 #include "archive.hh"
+#include "affinity.hh"
 #include "globals.hh"
 
 #include <sys/types.h>
@@ -15,7 +16,6 @@
 #include <unistd.h>
 #include <cstring>
 
-
 namespace nix {
 
 
@@ -71,8 +71,19 @@ void RemoteStore::openConnection(bool reserveSpace)
         if (GET_PROTOCOL_MAJOR(daemonVersion) != GET_PROTOCOL_MAJOR(PROTOCOL_VERSION))
             throw Error("Nix daemon protocol version not supported");
         writeInt(PROTOCOL_VERSION, to);
+
+        if (GET_PROTOCOL_MINOR(daemonVersion) >= 14) {
+            int cpu = lockToCurrentCPU();
+            if (cpu != -1) {
+                writeInt(1, to);
+                writeInt(cpu, to);
+            } else
+                writeInt(0, to);
+        }
+
         if (GET_PROTOCOL_MINOR(daemonVersion) >= 11)
             writeInt(reserveSpace, to);
+
         processStderr();
     }
     catch (Error & e) {