Merge branch 'master' into core-updates-frozen

3 files changed, 15 insertions, 7 deletions

diff --git a/nix/libstore/gc.cc b/nix/libstore/gc.cc
index e1d0765154..16519116e4 100644
--- a/nix/libstore/gc.cc
+++ b/nix/libstore/gc.cc
@@ -606,7 +606,9 @@ void LocalStore::removeUnusedLinks(const GCState & state)
             throw SysError(format("statting `%1%'") % path);
 #endif
 
-        if (st.st_nlink != 1) {
+	/* Drop links for files smaller than 'deduplicationMinSize', even if
+	   they have more than one hard link.  */
+        if (st.st_nlink != 1 && st.st_size >= deduplicationMinSize) {
             actualSize += st.st_size;
             unsharedSize += (st.st_nlink - 1) * st.st_size;
             continue;
diff --git a/nix/libstore/local-store.hh b/nix/libstore/local-store.hh
index 9ba37219da..20d3c3c893 100644
--- a/nix/libstore/local-store.hh
+++ b/nix/libstore/local-store.hh
@@ -292,4 +292,7 @@ void canonicaliseTimestampAndPermissions(const Path & path);
 
 MakeError(PathInUse, Error);
 
+/* Size below which a file is not considered for deduplication.  */
+extern const size_t deduplicationMinSize;
+
 }
diff --git a/nix/libstore/optimise-store.cc b/nix/libstore/optimise-store.cc
index eb303ab4c3..9fd6f3cb35 100644
--- a/nix/libstore/optimise-store.cc
+++ b/nix/libstore/optimise-store.cc
@@ -15,6 +15,9 @@
 
 namespace nix {
 
+/* Any file smaller than this is not considered for deduplication.
+   Keep in sync with (guix store deduplication).  */
+const size_t deduplicationMinSize = 8192;
 
 static void makeWritable(const Path & path)
 {
@@ -105,12 +108,12 @@ void LocalStore::optimisePath_(OptimiseStats & stats, const Path & path, InodeHa
         return;
     }
 
-    /* We can hard link regular files and maybe symlinks. */
-    if (!S_ISREG(st.st_mode)
-#if CAN_LINK_SYMLINK
-        && !S_ISLNK(st.st_mode)
-#endif
-        ) return;
+    /* We can hard link regular files (and maybe symlinks), but do that only
+       for files larger than some threshold.  This avoids adding too many
+       entries to '.links', which would slow down 'removeUnusedLinks' while
+       saving little space.  */
+    if (!S_ISREG(st.st_mode) || ((size_t) st.st_size) < deduplicationMinSize)
+	return;
 
     /* Sometimes SNAFUs can cause files in the store to be
        modified, in particular when running programs as root under