[buildd-tools-devel] Bug#606162: [PATCH] 15killprocs: Don’t run /bin/readlink for every process

[Anders Kaseorg]

Package: schroot
Version: 1.4.15-1
Tags: patch

/etc/schroot/setup.d/15killprocs has a loop that runs ‘readlink 
/proc/"$pid"/root’ for every process in the system.  I have a system with 
thousands of processes, and this loop makes schroot take about a minute to 
close a chroot.  I changed it to use the builtin -ef operator; now it 
takes about a second.

Anders

-- 8< --
From: Anders Kaseorg <andersk at ksplice.com>
Subject: [PATCH] setup.d: 15killprocs: Don’t run /bin/readlink for every process

On a system with thousands of processes, this loop took about a minute;
now it takes about a second.

Signed-off-by: Anders Kaseorg <andersk at ksplice.com>
---
 etc/setup.d/15killprocs |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/etc/setup.d/15killprocs b/etc/setup.d/15killprocs
index 88b9320..619035e 100755
--- a/etc/setup.d/15killprocs
+++ b/etc/setup.d/15killprocs
@@ -40,8 +40,7 @@ do_kill_all()
     info "Killing processes run inside $1"
     ls /proc | egrep '^[[:digit:]]+$' |
     while read pid; do
-        root=$(readlink /proc/"$pid"/root || true)
-        if [ "$root" = "$1" ]; then
+        if [ /proc/"$pid"/root -ef "$1" ]; then
             exe=$(readlink /proc/"$pid"/exe || true)
             info "Killing left-over pid $pid (${exe##$1})"
             info "  Sending SIGTERM to pid $pid"
-- 
1.7.3.3