wroclaw-git-backups/nix
1
0
Fork 0
mirror of https://github.com/NixOS/nix synced 2025-07-01 12:37:59 +02:00
Code Activity

Make the garbage collector more concurrent

Browse source 
Make the garbage collector more concurrent by deleting valid paths
outside the region where we're holding the global GC lock.  This
should greatly reduce the time during which new builds are blocked,
since the deletion accounts for the vast majority of the time spent in
the GC.

To ensure that this is safe, the valid paths are invalidated and
renamed to some arbitrary path while we're holding the lock.  This
ensures that we when we finally delete the path, it's not a (newly)
valid or locked path.
This commit is contained in:
Eelco Dolstra 2012-03-26 20:43:33 +02:00
parent 8be1979f1a
commit 117670be57
3 changed files with 47 additions and 20 deletions
Download patch file Download diff file Expand all files Collapse all files

51
src/libstore/gc.cc
View file

@ -1,6 +1,7 @@
#include "globals.hh"
#include "misc.hh"
#include "local-store.hh"
#include "immutable.hh"
#include <boost/shared_ptr.hpp>
@ -396,11 +397,11 @@ struct LocalStore::GCState
PathSet deleted;
PathSet live;
PathSet busy;
PathSet invalidated;
bool gcKeepOutputs;
bool gcKeepDerivations;
GCState(GCResults & results_) : results(results_)
{
}
unsigned long long bytesInvalidated;
GCState(GCResults & results_) : results(results_), bytesInvalidated(0) { }
};
@ -419,6 +420,16 @@ bool LocalStore::isActiveTempFile(const GCState & state,
}
void LocalStore::deleteGarbage(GCState & state, const Path & path)
{
printMsg(lvlInfo, format("deleting `%1%'") % path);
unsigned long long bytesFreed, blocksFreed;
deletePathWrapped(path, bytesFreed, blocksFreed);
state.results.bytesFreed += bytesFreed;
state.results.blocksFreed += blocksFreed;
}
bool LocalStore::tryToDelete(GCState & state, const Path & path)
{
checkInterrupt();
@ -502,15 +513,27 @@ bool LocalStore::tryToDelete(GCState & state, const Path & path)
/* The path is garbage, so delete it. */
if (shouldDelete(state.options.action)) {
printMsg(lvlInfo, format("deleting `%1%'") % path);
unsigned long long bytesFreed, blocksFreed;
deleteFromStore(path, bytesFreed, blocksFreed);
state.results.bytesFreed += bytesFreed;
state.results.blocksFreed += blocksFreed;
if (isValidPath(path)) {
/* If it's a valid path, invalidate it, rename it, and
schedule it for deletion. The renaming is to ensure
that later (when we're not holding the global GC lock)
we can delete the path without being afraid that the
path has become alive again. */
printMsg(lvlInfo, format("invalidating `%1%'") % path);
// Estimate the amount freed using the narSize field.
state.bytesInvalidated += queryPathInfo(path).narSize;
invalidatePathChecked(path);
Path tmp = (format("%1%-gc-%2%") % path % getpid()).str();
makeMutable(path.c_str());
if (rename(path.c_str(), tmp.c_str()))
throw SysError(format("unable to rename `%1%' to `%2%'") % path % tmp);
state.invalidated.insert(tmp);
} else
deleteGarbage(state, path);
if (state.options.maxFreed && state.results.bytesFreed > state.options.maxFreed) {
printMsg(lvlInfo, format("deleted more than %1% bytes; stopping") % state.options.maxFreed);
if (state.options.maxFreed && state.results.bytesFreed + state.bytesInvalidated > state.options.maxFreed) {
printMsg(lvlInfo, format("deleted or invalidated more than %1% bytes; stopping") % state.options.maxFreed);
throw GCLimitReached();
}
@ -635,6 +658,14 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
} catch (GCLimitReached & e) {
}
}
/* Allow other processes to add to the store from here on. */
fdGCLock.close();
/* Delete the invalidated paths now that the lock has been
released. */
foreach (PathSet::iterator, i, state.invalidated)
deleteGarbage(state, *i);
}