From: Jan Engelhardt <jengelh@linux01.gwdg.de>
To: linux-kernel@vger.kernel.org
Subject: keventd gives exceptional priority to usermode helpers
Date: Mon, 10 Jan 2005 11:28:38 +0100 (MET) [thread overview]
Message-ID: <Pine.LNX.4.61.0501101121370.11128@yvahk01.tjqt.qr> (raw)
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Hi,
on SUSE 9.2, we experienced that plugging in an USB stick slows the system
down considerably. In the end, I tracked (one half of the problem) down to
kernelspace, where keventd starts the /sbin/hotplug usermode helper with
priority -20. This is bad because hotplug, udev or the programs that ship with
the whole hotplug subsystem (possibly including SUSE's own scripts) require
some CPU -- and with nice -20 get it definitely.
keventd itself should stay at nice level -20, since it also spawns kreiserfsd,
just to name one. So the (attached) patch reprioritizes *user*mode
helpers/tasks back to nice 0.
Signed-off-by: Jan Engelhardt <jengelh@linux01.gwdg.de>
Jan Engelhardt
--
ENOSPC
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#==============================================================================
# Linux 2.6-HX MODIFICATION
# Copyright (C) Jan Engelhardt <jengelh [at] linux01 gwdg de>, 2004
# -- License restrictions apply (GPL2)
# -- For details see doc/GPL2.txt.
# http://linux01.org:2222/prog-hxtools.php
#==============================================================================
# File: utf8fix.diff
# Class:
#
# - udev and friends need a fair amount of CPU, and really bring down the
# system when they run -- usually in nice -20
# Fix it in that usermode helpers always get nice 0 by default
#
#------------------------------------------------------------------------------
diff -dpu usr_A/src/kotd/linux-2.6.8-20041204030200/kernel/kmod.c usr_B/src/kotd/linux-2.6.8-20041204030200/kernel/kmod.c
--- usr_A/src/kotd/linux-2.6.8-20041204030200/kernel/kmod.c 2004-12-06 14:28:44.000000000 +0100
+++ usr_B/src/kotd/linux-2.6.8-20041204030200/kernel/kmod.c 2005-01-06 11:44:04.130600000 +0100
@@ -165,6 +165,7 @@ static int ____call_usermodehelper(void
/* We can run anywhere, unlike our parent keventd(). */
set_cpus_allowed(current, CPU_MASK_ALL);
+ set_user_nice(current, 0);
retval = -EPERM;
if (current->fs->root)
next reply other threads:[~2005-01-10 10:28 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-01-10 10:28 Jan Engelhardt [this message]
2005-01-10 11:42 ` keventd gives exceptional priority to usermode helpers Chris Wright
2005-01-10 11:50 ` Jan Engelhardt
2005-01-11 12:11 ` Jan Engelhardt
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