From: Janne Johansson <j...@it.su.se>
Subject: Re: writing to usb very slow
Date: Mon, 18 Jan 2010 08:34:41 +0100
> You need to include the time to "sync" (or umount) after writing and
> deleting the files, otherwise you arent benchmarking the USB speed but
> rather how fast your caches are, since the time for rm -rf * will be
> spent at the umount (which you didnt include in the timing) instead,
> when flushing the pending writes/deletes.
Janne, thank you for your suggestion. I had a test again.
The environment was the same as the previous test. But copied/deleted
files were different (At this test, 4.6 kernel source tree and its
tarball were used).
Here's the result including the time of umount;
WRITING TIME
---------------------------------------------------
mount real user system
option write+umount write+umount write+umount
----- ----------------- --------------- ---------------
none 9m05.93s+0m07.37s 0m0.38s+0m0.00s 0m5.61s+0m0.41s
softdep 3m35.64s+0m35.71s 0m0.32s+0m0.00s 0m5.27s+0m0.49s
async 3m22.61s+0m05.90s 0m0.26s+0m0.00s 0m4.75s+0m0.37s
DELETING TIME
---------------------------------------------------
mount real user system
option delete+umount delete+umount delete+umount
----- ----------------- --------------- ---------------
none 4m21.23s+0m01.04s 0m0.03s+0m0.00s 0m1.71s+0m0.01s
softdep 0m02.10s+0m27.49s 0m0.04s+0m0.00s 0m0.43s+0m0.75s
async 0m02.40s+0m01.54s 0m0.10s+0m0.00s 0m0.44s+0m0.00s
However, mounting USB flash drive without any FFS option is very slow
at all.
