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Rate-limit the number of threads copying closures at the same time

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Having a hundred threads doing I/O at the same time is bad on magnetic
disks because of the excessive disk seeks. So allow only 4 threads to
copy closures in parallel.
This commit is contained in:
Eelco Dolstra
2015-06-23 01:49:14 +02:00
parent a317d24b29
commit 4db7c51b5c
5 changed files with 106 additions and 4 deletions
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17
src/hydra-queue-runner/build-remote.cc
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@ -60,6 +60,7 @@ static void openConnection(const string & sshName, const string & sshKey,
static void copyClosureTo(std::shared_ptr<StoreAPI> store,
FdSource & from, FdSink & to, const PathSet & paths,
TokenServer & copyClosureTokenServer,
bool useSubstitutes = false)
{
PathSet closure;
@ -88,6 +89,19 @@ static void copyClosureTo(std::shared_ptr<StoreAPI> store,
for (auto i = sorted.rbegin(); i != sorted.rend(); ++i)
if (present.find(*i) == present.end()) missing.push_back(*i);
/* Ensure that only a limited number of threads can copy closures
at the same time. However, proceed anyway after a timeout to
prevent starvation by a handful of really huge closures. */
time_t start = time(0);
int timeout = 60 * (10 + rand() % 5);
auto token(copyClosureTokenServer.get(timeout));
time_t stop = time(0);
if (token())
printMsg(lvlDebug, format("got copy closure token after %1%s") % (stop - start));
else
printMsg(lvlDebug, format("dit not get copy closure token after %1%s") % (stop - start));
printMsg(lvlDebug, format("sending %1% missing paths") % missing.size());
writeInt(cmdImportPaths, to);
@ -114,6 +128,7 @@ void buildRemote(std::shared_ptr<StoreAPI> store,
const string & sshName, const string & sshKey,
const Path & drvPath, const Derivation & drv,
const nix::Path & logDir, unsigned int maxSilentTime, unsigned int buildTimeout,
TokenServer & copyClosureTokenServer,
RemoteResult & result, counter & nrStepsBuilding)
{
string base = baseNameOf(drvPath);
@ -163,7 +178,7 @@ void buildRemote(std::shared_ptr<StoreAPI> store,
/* Copy the input closure. */
printMsg(lvlDebug, format("sending closure of ‘%1%’ to ‘%2%’") % drvPath % sshName);
copyClosureTo(store, from, to, inputs);
copyClosureTo(store, from, to, inputs, copyClosureTokenServer);
autoDelete.cancel();