Bug 1018474

Summary: Can't set vm.nr_pdflush_threads= variable from kernel
Product: [Fedora] Fedora Reporter: Marian <corcodel.marian>
Component: kernelAssignee: Kernel Maintainer List <kernel-maint>
Status: CLOSED NOTABUG QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 19CC: gansalmon, itamar, jonathan, kernel-maint, madhu.chinakonda, marcelo.barbosa
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Target Release: ---   
Hardware: x86_64   
OS: Linux   
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Fixed In Version: Doc Type: Bug Fix
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Clone Of: Environment:
Last Closed: 2013-10-12 12:42:29 UTC Type: Bug
Regression: --- Mount Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description Marian 2013-10-12 11:28:14 UTC 
Description of problem:


Version-Release number of selected component (if applicable):
kernel 3.11.1-200.fc19.x86_64

How reproducible:


Steps to Reproduce:
1.Run as root sysctl -w vm.nr_pdflush_threads=1
2.sysctl -a 
3.

Actual results:
Variable vm.nr_pdflush_threads=0 

Expected results:
vm.nr_pdflush_threads=1

Additional info:
Comment 1 Josh Boyer 2013-10-12 12:42:29 UTC 
That's because it's been obsolete for a while.  per-BDI flusher threads were introduced in 2.6 and pdflush isn't used anymore.  In 3.6, the following commit made the nr_pdflush_threads sysctl obsolete:

commit 3965c9ae47d64aadf6f13b6fcd37767b83c0689a
Author: Wanpeng Li <liwp.ibm.com>
Date:   Tue Jul 31 16:41:52 2012 -0700

    mm: prepare for removal of obsolete /proc/sys/vm/nr_pdflush_threads
    
    Since per-BDI flusher threads were introduced in 2.6, the pdflush
    mechanism is not used any more.  But the old interface exported through
    /proc/sys/vm/nr_pdflush_threads still exists and is obviously useless.
    
    For back-compatibility, printk warning information and return 2 to notify
    the users that the interface is removed.
    
    Signed-off-by: Wanpeng Li <liwp.ibm.com>
    Cc: Wu Fengguang <fengguang.wu>
    Signed-off-by: Andrew Morton <akpm>
    Signed-off-by: Linus Torvalds <torvalds>