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Bug 726437 - Disk write cache flushes are no longer logged in blktrace
Summary: Disk write cache flushes are no longer logged in blktrace
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: kernel
Version: 6.2
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: beta
: 6.2
Assignee: Jeff Moyer
QA Contact: Gris Ge
URL:
Whiteboard:
Depends On: 736399
Blocks: 743047
TreeView+ depends on / blocked
 
Reported: 2011-07-28 15:13 UTC by Jeff Moyer
Modified: 2011-12-06 13:55 UTC (History)
5 users (show)

Fixed In Version: kernel-2.6.32-197.el6
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2011-12-06 13:55:06 UTC
Target Upstream Version:
Embargoed:


Attachments (Terms of Use)
add BIO_RW_FLUSH to the list of bits to check when flagging barrier requests (438 bytes, patch)
2011-07-28 15:13 UTC, Jeff Moyer
no flags Details | Diff
fix up barrier reporting in blktrace (1.34 KB, patch)
2011-07-28 18:03 UTC, Jeff Moyer
no flags Details | Diff


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2011:1530 0 normal SHIPPED_LIVE Moderate: Red Hat Enterprise Linux 6 kernel security, bug fix and enhancement update 2011-12-06 01:45:35 UTC

Description Jeff Moyer 2011-07-28 15:13:32 UTC
Created attachment 515749 [details]
add BIO_RW_FLUSH to the list of bits to check when flagging barrier requests

Description of problem:
blktrace will no longer display when write cache flushes are sent to the disk, due to the flush/fua conversion.  It was missing a simple conditional in kernel/trace/blktrace.c.  Without this information, it will be difficult to diagnose performance issues in the field.

Version-Release number of selected component (if applicable):


How reproducible:
100%

Steps to Reproduce:
1. run a workload that generates fsyncs
2. record blktrace data
3. observe the absense of WBS requests

Comment 2 RHEL Program Management 2011-07-28 15:30:30 UTC
This request was evaluated by Red Hat Product Management for inclusion
in a Red Hat Enterprise Linux maintenance release. Product Management has 
requested further review of this request by Red Hat Engineering, for potential
inclusion in a Red Hat Enterprise Linux Update release for currently deployed 
products. This request is not yet committed for inclusion in an Update release.

Comment 3 Jeff Moyer 2011-07-28 18:03:54 UTC
Created attachment 515778 [details]
fix up barrier reporting in blktrace

This patch reports 'B' in the blktrace output when the flush flag is set in a request or bio.  It also fixes up the translation between blk_add_trace_rq and __blk_add_trace for barrier and discard requests (the latter function checks for BIO_RW_* while the former was setting REQ_*).

Comment 9 Aristeu Rozanski 2011-09-14 21:21:49 UTC
Patch(es) available on kernel-2.6.32-197.el6

Comment 12 Gris Ge 2011-09-16 05:08:35 UTC
kernel 197 with blktrace-1.0.1-6.el6 provide write cache flushes:
========
  8,1    0    20713     2.418776737   737  I FWFS 295626 + 2 [jbd2/sda1-8]
========

I am new to FLUSH/FUA, if this is not what we fix in this bug, correct me.

Thanks.

VERIFY this bug.

Comment 13 errata-xmlrpc 2011-12-06 13:55:06 UTC
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2011-1530.html


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