Storage Speed on the PandaBoard Revisited (Again)

Since my last post, I took a short vacation and I've been helping in the Virtual Fedora Activity Days (VFAD) to rebuild packages for Fedora 15 hardfp (hardware floating point).

Research into the slow storage speeds on the PandaBoard (and other Cortex-ARM9 systems) has continued and a patch set developed to hopefully improve the situation.  David Marlin built a 2.6.40.3-2.02.fc13.armv7l.omap kernel with the patch set, so I downloaded a copy and ran bonnie++ again.

The results were mixed for the SD card.  Sequential reads had a nice improvement, but sequential output and random seeks took a big hit.  The random seek times are particularly worrisome with an increase from 663ms to 76023ms!  Something doesn't seem right.

The USB hard drive, though, saw some nice improvements overall. Sequential write latencies dropped from 5.8 seconds down to 0.38 seconds and throughput more than doubled: 9 MiB/s vs 23 MiB/s!  Sequential reads latencies increased a bit, but throughput again more than doubled: 12 MiB/s vs 27 MiB/s!  Random seeks also saw a nice improvement from 7.6s down to 4.9s.

Version 1.96		Sequential Output						Sequential Input				Random Seeks
	Size	Per Char		Block		Rewrite		Per Char		Block
		K/sec	% CPU	K/sec	% CPU	K/sec	% CPU	K/sec	% CPU	K/sec	% CPU	/sec	% CPU
SD Card 2.6.35-g6d019da-dirty	2G	41	93	3125	5	3371	4	336	99	17598	15	27.4	1
	Latency	1168ms		33487ms		32391ms		44466us		2628ms		663ms
SD Card 2.6.40.3-2.02.fc13.armv7l.omap	2G	22	65	1862	4	2544	3	339	99	19626	16	15.6	1
	Latency	2793ms		29928ms		39111ms		50446us		665ms		76023ms
USB HD 2.6.35-g6d019da-dirty	2G	43	99	9017	16	4538	6	369	99	12357	9	93.9	6
	Latency	215ms		5849ms		5889ms		52858us		108ms		7643ms
USB HD 2.6.40.3-2.02.fc13.armv7l.omap	2G	39	99	23519	26	11118	15	327	99	27314	18	150.6	12
	Latency	322ms		383ms		341ms		54567us		697ms		4910ms

I also tried a simple test with hdparm as shown on lwn.net:

[root@fedora-arm ~]# uname -r
2.6.40.3-2.02.fc13.armv7l.omap

[root@fedora-arm ~]# hdparm -t /dev/mmcblk0p4

/dev/mmcblk0p4:
 Timing buffered disk reads:   50 MB in  3.10 seconds =  16.11 MB/sec

[root@fedora-arm ~]# hdparm -t /dev/sda1

/dev/sda1:
 Timing buffered disk reads:   66 MB in  3.05 seconds =  21.64 MB/sec

Compared to the older kerrnel:

[root@fedora-arm ~]# uname -r
2.6.35-g6d019da-dirty

[root@fedora-arm ~]# hdparm -t /dev/mmcblk0p4

/dev/mmcblk0p4:
 Timing buffered disk reads:   50 MB in  3.09 seconds =  16.20 MB/sec

[root@fedora-arm ~]# hdparm -t /dev/sda1

/dev/sda1:
 Timing buffered disk reads:   26 MB in  3.04 seconds =   8.56 MB/sec


The SD card's performance is about the same, but the USB hard drive is much faster with the new patch!