From mboxrd@z Thu Jan 1 00:00:00 1970
From: bugzilla-daemon@bugzilla.kernel.org
Subject: [Bug 71641] Unreasonable performance degradation in ext4 with full
data journaling
Date: Wed, 19 Mar 2014 09:35:03 +0000
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https://bugzilla.kernel.org/show_bug.cgi?id=71641
--- Comment #3 from Chia-Hung Chang ---
Test command : dd if=/dev/zero of=/share/CACHEDEV2_DATA/orderno5G bs=1M
count=5120
The results of block trace can be download as follow.
https://dl.dropboxusercontent.com/u/32959539/blktrace_original_data.7z
The results of btt can be download as follow.
https://dl.dropboxusercontent.com/u/32959539/blktrace_output.7z
There are three folders:
/journal -->ext4,data=journal with 375MB/s
/order_delalloc -->ext4,data=ordered,delalloc with 937MB/s
/order_nodelalloc -->ext4,data=ordered,nodelalloc with 353MB/s
The size of write request with data=ordered,delalloc is 64k mostly.
The size of write requests with data=journal and data=ordered,nodelalloc are 4k
mostly.
If we observe the average Q2Q in btt results, which means time interval between
requests, we have
/journal 0.00081
/order_nodelalloc 0.00031
It seems to be the reason of performance degradation.
Is any one know why the time interval of requests is significantly longer with
data=journal?
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