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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
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.
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_*).
Patch(es) available on kernel-2.6.32-197.el6
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.
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