diff --git a/src/parallel b/src/parallel
index 483a2c9c..e1f1982c 100755
--- a/src/parallel
+++ b/src/parallel
@@ -1550,10 +1550,10 @@ sub find_compression_program {
     #   $compress_program = compress program with options
     #   $decompress_program = decompress program with options
 
-    # Search for these. Sorted by speed on 16 core
-    # parallel -j1  --joblog jl --arg-sep ,  parallel --compress-program \'{3}" "-{2}\' cat ::: gz '>'/dev/null , 1 2 3 ,  {1..3} , lz4 lzop pigz pxz gzip plzip pbzip2 lzma xz lzip bzip2
+    # Search for these. Sorted by speed on 20 core
+    # parallel -j1  --joblog jl --arg-sep ,  parallel --compress-program \'{3}" "-{2}\' cat ::: gz '>'/dev/null , 1 2 3 ,  {1..3} , zstd clzip lz4 lzop pigz pxz gzip plzip pbzip2 lzma xz lzip bzip2
     # sort -nk4 jl
-    my @prg = qw(lz4 pigz lzop plzip pbzip2 pxz gzip lzma xz bzip2 lzip);
+    my @prg = qw(lz4 lzop pbzip2 pigz plzip lzip gzip pxz lzma xz bzip2);
     for my $p (@prg) {
 	if(which($p)) {
 	    return ("$p -c -1","$p -dc");
@@ -4311,6 +4311,13 @@ sub reap_usleep {
     #   $ms*1.1 if no children reaped
     my $ms = shift;
     if(reaper()) {
+	if(not $Global::total_completed % 100) {
+	    if($opt::timeout) {
+		# Force cleaning the timeout queue for every 1000 jobs
+		# Fixes potential memleak
+		$Global::timeoutq->process_timeouts();
+	    }
+	}
 	# Sleep exponentially shorter (1/2^n) if a job finished
 	return $ms/2+0.001;
     } else {
@@ -6278,7 +6285,7 @@ sub slot {
 
 sub free_slot {
     my $self = shift;
-    return $self->{'commandline'}->free_slot();
+    push @Global::slots, $self->slot();
 }
 
 {
@@ -8479,28 +8486,23 @@ sub set_seq {
 
 {
     my $max_slot_number;
-    my @slots;
 
     sub slot {
 	# Find the number of a free job slot and return it
+        # Uses:
+        #   @Global::slots - list with free jobslots
 	# Returns:
 	#   $jobslot = number of jobslot
 	my $self = shift;
 	if(not $self->{'slot'}) {
-	    if(not @slots) {
+	    if(not @Global::slots) {
 		# $max_slot_number will typically be $Global::max_jobs_running
-		push @slots, ++$max_slot_number;
+		push @Global::slots, ++$Global::max_slot_number;
 	    }
-	    $self->{'slot'} = shift @slots;
+	    $self->{'slot'} = shift @Global::slots;
 	}
 	return $self->{'slot'};
     }
-
-    sub free_slot {
-	# Make this slot available again
-	my $self = shift;
-	push @slots, $self->{'slot'};
-    }
 }
 
 sub populate {