If threads are configured explicit to a positive number, obey it.

If not scale it with num_cores/8 capped i the range [1, 4].
Let default configured value be 0 (unset) instead of 4.

3 files changed, 11 insertions, 4 deletions

diff --git a/searchlib/src/vespa/searchlib/config/translogserver.def b/searchlib/src/vespa/searchlib/config/translogserver.def
index 6a8a1201d36..c5e271a047b 100644
--- a/searchlib/src/vespa/searchlib/config/translogserver.def
+++ b/searchlib/src/vespa/searchlib/config/translogserver.def
@@ -18,7 +18,7 @@ basedir string default="tmp" restart
 usefsync bool default=true
 
 ##Number of threads available for visiting/subscription.
-maxthreads int default=4 restart
+maxthreads int default=0 restart
 
 ##Default crc method used
 crcmethod enum {ccitt_crc32, xxh64} default=xxh64
diff --git a/searchlib/src/vespa/searchlib/transactionlog/translogserverapp.cpp b/searchlib/src/vespa/searchlib/transactionlog/translogserverapp.cpp
index a9b0f96c4db..927047cecaa 100644
--- a/searchlib/src/vespa/searchlib/transactionlog/translogserverapp.cpp
+++ b/searchlib/src/vespa/searchlib/transactionlog/translogserverapp.cpp
@@ -79,17 +79,24 @@ logReconfig(const searchlib::TranslogserverConfig & cfg, const DomainConfig & dc
         dcfg.getPartSizeLimit(), dcfg.getChunkSizeLimit());
 }
 
+size_t
+derive_num_threads(uint32_t configured_cores, uint32_t actual_cores) {
+    return (configured_cores > 0)
+        ? configured_cores
+        : std::max(1u, std::min(4u, actual_cores/8));
+}
+
 }
 
 void
-TransLogServerApp::start()
+TransLogServerApp::start(uint32_t num_cores)
 {
     std::lock_guard<std::mutex> guard(_lock);
     auto c = _tlsConfig.get();
     DomainConfig domainConfig = getDomainConfig(*c);
     logReconfig(*c, domainConfig);
    _tls = std::make_shared<TransLogServer>(c->servername, c->listenport, c->basedir, _fileHeaderContext,
-                                            domainConfig, c->maxthreads);
+                                            domainConfig, derive_num_threads(c->maxthreads, num_cores));
 }
 
 TransLogServerApp::~TransLogServerApp()
diff --git a/searchlib/src/vespa/searchlib/transactionlog/translogserverapp.h b/searchlib/src/vespa/searchlib/transactionlog/translogserverapp.h
index c5854958b9e..ccd207ed6d1 100644
--- a/searchlib/src/vespa/searchlib/transactionlog/translogserverapp.h
+++ b/searchlib/src/vespa/searchlib/transactionlog/translogserverapp.h
@@ -32,7 +32,7 @@ public:
 
     TransLogServer::SP getTransLogServer() const;
 
-    void start();
+    void start(uint32_t num_cores);
 };
 
 }