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daemon: Buffer data sent to clients by the 'export-path' RPC. 

Before that we'd have STDERR_WRITE round trips for very small amounts of
data, ranging from a few bytes for the metadata of nars to the size of
one file being exported.

With this change, something like:

  guix archive --export /gnu/store/5rrsbaghh5ix1vjcicsl60gsxilhjnf2-coreutils-8.25 | dd of=/dev/null

reports a throughput of 35 MB/s instead of 25 MB/s before.

* nix/nix-daemon/nix-daemon.cc (TunnelSink): Inherit from 'BufferedSink'
rather than 'Sink'.  Rename 'operator ()' to 'write'.
(performOp) <wopExportPath>: Add 'sink.flush' call.
This commit is contained in:
Ludovic Courtès 2016-12-01 22:53:37 +01:00
parent 0b72475301
commit 9a8f9f84cc
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1 changed files with 4 additions and 3 deletions
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nix/nix-daemon/nix-daemon.cc
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@ -203,11 +203,11 @@ static void stopWork(bool success = true, const string & msg = "", unsigned int
}
struct TunnelSink : Sink
struct TunnelSink : BufferedSink
{
Sink & to;
TunnelSink(Sink & to) : to(to) { }
virtual void operator () (const unsigned char * data, size_t len)
TunnelSink(Sink & to) : BufferedSink(64 * 1024), to(to) { }
virtual void write(const unsigned char * data, size_t len)
{
writeInt(STDERR_WRITE, to);
writeString(data, len, to);
@ -433,6 +433,7 @@ static void performOp(bool trusted, unsigned int clientVersion,
startWork();
TunnelSink sink(to);
store->exportPath(path, sign, sink);
sink.flush();
stopWork();
writeInt(1, to);
break;