a pointer to a Value, rather than the Value directly. This improves
the effectiveness of garbage collection a lot: if the Value is
stored inside the set directly, then any live pointer to the Value
causes all other attributes in the set to be live as well.
race with other processes that add new referrers to a path,
resulting in the garbage collector crashing with "foreign key
constraint failed". (Nix/4)
* Make --gc --print-dead etc. interruptible.
because it defines _FILE_OFFSET_BITS. Without this, on
OpenSolaris the system headers define it to be 32, and then
the 32-bit stat() ends up being called with a 64-bit "struct
stat", or vice versa.
This also ensures that we get 64-bit file sizes everywhere.
* Remove the redundant call to stat() in parseExprFromFile().
The file cannot be a symlink because that's the exit condition
of the loop before.
exception handler, otherwise throw an exception. We need to ignore
write errors in exception handlers to ensure that cleanup code runs
to completion if the other side of stderr has been closed
unexpectedly.
* If a path has disappeared, check its referrers first, and don't try
to invalidate paths that have valid referrers. Otherwise we get a
foreign key constraint violation.
* Read the whole Nix store directory instead of statting each valid
path, which is slower.
* Acquire the global GC lock.
hook script proper, and the stdout/stderr of the builder. Only the
latter should be saved in /nix/var/log/nix/drvs.
* Allow the verbosity to be set through an option.
* Added a flag --quiet to lower the verbosity level.
it requires a certain feature on the build machine, e.g.
requiredSystemFeatures = [ "kvm" ];
We need this in Hydra to make sure that builds that require KVM
support are forwarded to machines that have KVM support. Probably
this should also be enforced for local builds.
the hook every time we want to ask whether we can run a remote build
(which can be very often), we now reuse a hook process for answering
those queries until it accepts a build. So if there are N
derivations to be built, at most N hooks will be started.
because Berkeley DB needed it on some platforms, but we don't use
BDB anymore.
On FreeBSD, if you link against pthreads, then the main thread gets
a 2 MB stack which cannot be overriden (it ignores "ulimit -s"):
http://www.mail-archive.com/freebsd-hackers@freebsd.org/msg62445.html
This is not enough for Nix. For instance, the garbage collector can
fail if there is a pathologically deep chain of references
(http://hydra.nixos.org/build/556199). 2 MB is also not enough for
many Nix expressions.
Arguably the garbage collector shouldn't use recursion, because in
NixOS unprivileged users can DOS the garbage collector by creating a
sufficiently deeply nested chain of references. But getting rid of
recursion is a bit harder.
faster than the old mode when fsyncs are enabled, because it only
performs an fsync() when doing a checkpoint, rather than at every
commit. Some timings for doing a "nix-instantiate /etc/nixos/nixos
-A system" after modifying the stdenv setup script:
42.5s - SQLite 3.6.23 with truncate mode and fsync
3.4s - SQLite 3.6.23 with truncate mode and no fsync
32.1s - SQLite 3.7.0 with truncate mode and fsync
16.8s - SQLite 3.7.0 with WAL mode and fsync, auto-checkpoint
every 1000 pages
8.3s - SQLite 3.7.0 with WAL mode and fsync, auto-checkpoint
every 8192 pages
1.7s - SQLite 3.7.0 with WAL mode and no fsync
The default is now to use WAL mode with fsyncs. Because WAL doesn't
work on remote filesystems such as NFS (as it uses shared memory),
truncate mode can be re-enabled by setting the "use-sqlite-wal"
option to false.
using the build hook mechanism, by setting the derivation attribute
"preferLocalBuild" to true. This has a few use cases:
- The user environment builder. Since it just creates a bunch of
symlinks without much computation, there is no reason to do it
remotely. In fact, doing it remotely requires the entire closure
of the user environment to be copied to the remote machine, which
is extremely wasteful.
- `fetchurl'. Performing the download on a remote machine and then
copying it to the local machine involves twice as much network
traffic as performing the download locally, and doesn't save any
CPU cycles on the local machine.
instance) "nix-env -i wine" works on x86_64-linux, even though Wine
is built on i686-linux. In the event that there are multiple
matching derivations, prefer those built for the current system.
