tvl-depot/src/libutil/affinity.hh
Eelco Dolstra a583a2bc59 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
2013-08-07 14:02:04 +02:00

9 lines
111 B
C++

#pragma once
namespace nix {
void setAffinityTo(int cpu);
int lockToCurrentCPU();
void restoreAffinity();
}