From d704b59550390528dd57f11d43f3420601fccd5c Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Fri, 4 Nov 2016 14:33:18 +0000
Subject: [PATCH] check really parallel

---
 check | 49 +++++++++++++++++++++++++++++++++----------------
 1 file changed, 33 insertions(+), 16 deletions(-)

diff --git a/check b/check
index 7293371..b9eac53 100755
--- a/check
+++ b/check
@@ -2,13 +2,30 @@
 set -e
 set -o pipefail
 
+cpus=$(
+	perl -we '
+	    use strict;
+	    require Sys::CPU;
+	    my $ncpus = Sys::CPU::cpu_count();
+	    $ncpus *= 1.5;
+            print join " ", (0 .. $ncpus-1) or die $!;
+	    print "\n" or die $!;
+	' ||
+	echo 0 1 2
+)
+
 rm -rf stunt
 mkdir stunt
 cd stunt
 
+for cpu in $cpus; do
+	mkdir c$cpu
+	(cd c$cpu
+	 git init)
+done
+
 #exec 3<&0 </dev/null
 
-git init
 #git commit --allow-empty -m 'Test object'
 #head=`git rev-parse HEAD`
 
@@ -22,20 +39,17 @@ perl -we '
     our $batch=0;
     our @tasks;
 
-    my $ncpus = eval {
-        require Sys::CPU;
-	Sys::CPU::cpu_count();
-    } // 3;
+    my @freecpus = qw('"$cpus"');
 
-$ncpus=1;
-    print STDERR "check using $ncpus cpus\n";
+    print STDERR "check using cpus @freecpus\n";
 
     sub await_task () {
-	my ($pid, $oldbatch) = @{ shift @tasks };
+	my ($pid, $cpu, $oldbatch) = @{ shift @tasks };
 	waitpid $pid, 0 == $pid or die $!;
 	die "$oldbatch $?" if $?;
-	unlink $oldbatch or die "$oldbatch $!";
-        print STDERR "check completed $oldbatch [$pid]\n";
+	unlink "b$oldbatch" or die "$oldbatch $!";
+        print STDERR "check completed $oldbatch [$pid] #$cpu\n";
+	push @freecpus, $cpu;
     }
 
     sub complete_batch () {
@@ -45,19 +59,22 @@ $ncpus=1;
 
         print STDERR "check closing $batch ($count)\n";
 
-	await_task if @tasks >= $ncpus;
+	await_task unless @freecpus;
+
+	my $cpu = shift @freecpus;
 
 	my $pid = fork // die $!;
 	if (!$pid) {
 	    close STDIN;
 #            seek STDIN,0,1;
 #            flush STDIN;
-	    open STDIN, "<", $batch or die $batch;
-	    exec qw(git update-ref --stdin);
+	    open STDIN, "<", "b$batch" or die $batch;
+	    chdir "c$cpu" or die "$cpu $!";
+	    exec qw(eatmydata git update-ref --stdin);
 	    die $!;
 	}
-        print STDERR "check spawned $batch ($count) [$pid]\n";
-    	push @tasks, [ $pid, $batch ];
+        print STDERR "check spawned $batch ($count) [$pid] #$cpu\n";
+    	push @tasks, [ $pid, $cpu, $batch ];
 	$batch++;
 	$file = undef;
 	$count = 0;
@@ -65,7 +82,7 @@ $ncpus=1;
 
     while (<>) {
 #print STDERR ">$_<\n";
-        $file ||= new IO::File $batch, ">" or die $!;
+        $file ||= new IO::File "b$batch", ">" or die $!;
         chomp;
 	print $file "delete refs/tags/$_\n" or die $!;
 	$count++ < 100000 or complete_batch;
-- 
2.30.2