1 files changed, 39 insertions, 7 deletions

diff --git a/src/libutil/compression.cc b/src/libutil/compression.cc
index 5e2631ba3408..470c925ed7a6 100644
--- a/src/libutil/compression.cc
+++ b/src/libutil/compression.cc
@@ -1,6 +1,7 @@
 #include "compression.hh"
 #include "util.hh"
 #include "finally.hh"
+#include "logging.hh"
 
 #include <lzma.h>
 #include <bzlib.h>
@@ -151,10 +152,10 @@ static ref<std::string> decompressBrotli(const std::string & in)
 #endif // HAVE_BROTLI
 }
 
-ref<std::string> compress(const std::string & method, const std::string & in)
+ref<std::string> compress(const std::string & method, const std::string & in, const bool parallel)
 {
     StringSink ssink;
-    auto sink = makeCompressionSink(method, ssink);
+    auto sink = makeCompressionSink(method, ssink, parallel);
     (*sink)(in);
     sink->finish();
     return ssink.s;
@@ -189,10 +190,9 @@ struct XzSink : CompressionSink
     lzma_stream strm = LZMA_STREAM_INIT;
     bool finished = false;
 
-    XzSink(Sink & nextSink) : nextSink(nextSink)
-    {
-        lzma_ret ret = lzma_easy_encoder(
-            &strm, 6, LZMA_CHECK_CRC64);
+    template <typename F>
+    XzSink(Sink & nextSink, F&& initEncoder) : nextSink(nextSink) {
+        lzma_ret ret = initEncoder();
         if (ret != LZMA_OK)
             throw CompressionError("unable to initialise lzma encoder");
         // FIXME: apply the x86 BCJ filter?
@@ -200,6 +200,9 @@ struct XzSink : CompressionSink
         strm.next_out = outbuf;
         strm.avail_out = sizeof(outbuf);
     }
+    XzSink(Sink & nextSink) : XzSink(nextSink, [this]() {
+        return lzma_easy_encoder(&strm, 6, LZMA_CHECK_CRC64);
+    }) {}
 
     ~XzSink()
     {
@@ -253,6 +256,27 @@ struct XzSink : CompressionSink
     }
 };
 
+#ifdef HAVE_LZMA_MT
+struct ParallelXzSink : public XzSink
+{
+  ParallelXzSink(Sink &nextSink) : XzSink(nextSink, [this]() {
+        lzma_mt mt_options = {};
+        mt_options.flags = 0;
+        mt_options.timeout = 300; // Using the same setting as the xz cmd line
+        mt_options.preset = LZMA_PRESET_DEFAULT;
+        mt_options.filters = NULL;
+        mt_options.check = LZMA_CHECK_CRC64;
+        mt_options.threads = lzma_cputhreads();
+        mt_options.block_size = 0;
+        if (mt_options.threads == 0)
+            mt_options.threads = 1;
+        // FIXME: maybe use lzma_stream_encoder_mt_memusage() to control the
+        // number of threads.
+        return lzma_stream_encoder_mt(&strm, &mt_options);
+  }) {}
+};
+#endif
+
 struct BzipSink : CompressionSink
 {
     Sink & nextSink;
@@ -449,8 +473,16 @@ struct BrotliSink : CompressionSink
 };
 #endif // HAVE_BROTLI
 
-ref<CompressionSink> makeCompressionSink(const std::string & method, Sink & nextSink)
+ref<CompressionSink> makeCompressionSink(const std::string & method, Sink & nextSink, const bool parallel)
 {
+    if (parallel) {
+#ifdef HAVE_LZMA_MT
+        if (method == "xz")
+            return make_ref<ParallelXzSink>(nextSink);
+#endif
+        printMsg(lvlError, format("Warning: parallel compression requested but not supported for method '%1%', falling back to single-threaded compression") % method);
+    }
+
     if (method == "none")
         return make_ref<NoneSink>(nextSink);
     else if (method == "xz")