Reduce substitution memory consumption

copyStorePath() now pipes the output of srcStore->narFromPath()
directly into dstStore->addToStore(). The sink used by the former is
converted into a source usable by the latter using
boost::coroutine2. This is based on [1].

This reduces the maximum resident size of

  $ nix build --store ~/my-nix/ /nix/store/b0zlxla7dmy1iwc3g459rjznx59797xy-binutils-2.28.1 --substituters file:///tmp/binary-cache-xz/ --no-require-sigs

from 418592 KiB to 53416 KiB. (The previous commit also reduced the
runtime from ~4.2s to ~3.4s, not sure why.) A further improvement will
be to download files into a Sink.

[1] https://github.com/NixOS/nix/compare/master...Mathnerd314:dump-fix-coroutine#diff-dcbcac55a634031f9cc73707da6e4b18

Issue #1969.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/nix-daemon/nix-daemon.cc b/src/nix-daemon/nix-daemon.cc
index 30e2b54552ee..50258018aef4 100644
--- a/src/nix-daemon/nix-daemon.cc
+++ b/src/nix-daemon/nix-daemon.cc
@@ -695,7 +695,7 @@ static void performOp(TunnelLogger * logger, ref<LocalStore> store,
         parseDump(tee, tee.source);
 
         logger->startWork();
-        store->addToStore(info, tee.source.data, (RepairFlag) repair,
+        store.cast<Store>()->addToStore(info, tee.source.data, (RepairFlag) repair,
             dontCheckSigs ? NoCheckSigs : CheckSigs, nullptr);
         logger->stopWork();
         break;