1. Advanced XIP Filing System
AXFS
Advanced XIP Filing System
Jared Hulbert
Numonyx
April 15, 2008
Source1: This presentation, Machine #?
Screens: Output to Left and Right Main Screens, Left Confidence Screen
Notes: This presentation will be controlled by Ed Doller
Source2: Live video
Screens: Main Middle Screen
Notes:
Source3: This presentation, Machine #?
Screens: Right Confidence Screen
Notes: same as Source1 with “1 click” ahead so Ed can see upcoming animations and/or foils

2. Agenda Goal/History Features Architecture Test Results
Kernel Integration

3. Project Goals Supportable solution for application XIP
Fine grained control on compression
Flexible use of all system memories
NOR, NAND, RAM

4. What is Application XIP?
eXecute In Place of userspace code
Run code from where it is stored on Flash
Saves memory
No paging = higher performance
“I thought the kernel supported XIP?”
Yes, for ext2 with specialized hardware
Yes, for kernel code segments (xipImage)

5. Why a New Filesystem? CRAMFS XIP patches used to work BUT...
~9 years old and haven’t been merged???
patches broke, real bad, every year
File level compression choice
SquashFS? New, better compression BUT…
Block device oriented architecture
Didn’t see how to fit new concepts into arch

6. Features Basic Attributes Compression Flexible Mount Tools Read-only
64bit
Designed with CE requirements in mind
Compression
4KB-4GB compression block size
Page by page uncompression map for XIP
Flexible Mount
MTD (NAND/NOR)
block device
split across XIP NOR and non-XIP NAND
Tools
GPL mkfs.axfs
Supported propriety image builder available

7. Onmedia Format Superblock Region Descriptor Regions
Points to many region descriptor
Region Descriptor
Describes / points to one region
Regions
Each data type / table has own region
permissions, file names, file node info, file data, etc.
Region Descriptor
Region Descriptor
Region Descriptor
File Info
XIP Region
Compressed Region

8. Data Flow inode Node Index Node Type Table XIP Region Index 0 Index 1
Compressed
Compressed Region
cblock Offset Table
Uncompressed cblock
Index 0
Index 2
Index 1
Index 3
cnode Offset Table
Index 3
Application Virtual Pages

9. Mount Options mount –t axfs –o block_dev=/dev/mtd1 /dev/mtd0 /mnt/axfs
/dev/sda0
~/file.axfs
(-o loop)
/dev/mtd0
(NAND)
/dev/mtd0
(NOR)
/dev/mtd0
(NOR)
AXFS
Image
AXFS
Image
AXFS
Image
AXFS
Image
AXFS
Image
Part 1
(MMAP)
/dev/mtd1
(NAND)
AXFS
Image
Part 2
(IO)

10. Image Size Comparison
~1 year old Opie build from OpenEmbedded

11. Total Memory Used

12. Fitting into Real Chips

13. Performance: direct comparison
PXA270
Linux
Opie build
520 MHz (CPU)
208 MHz (memory clock)
104 MHz (SDRAM bus)
52 MHz (NOR flash bus)
xipImage
CONFIG_PREEMPT=y
MTD updated to Sept 25 git pull
“mem=24MB” in kernel commandline
OpenEmbedded
~1 year old

14. Performance: Direct Comparison
Root Filing System Comparison Video at:

15. Performance: realistic comparison
Started with commercial phone
PXA270, 48MB RAM, 32MB NOR, 96MB NAND
297 MHz (CPU) / 97 MHz (SDRAM bus) /48 MHz (NOR flash bus)
code in CRAMFS from NOR
data in NAND
“XIP”
code in AXFS from NOR
“SnD”
code in CRAMFS from NAND
data on NAND

16. Performance: realistic comparison
XIP vs. SND: Realistic Performance Comparison Video at:

17. Kernel Integration Status
Patches
VM_MIXEDMAP / pageless XIP patchset
just got in –mm tree
2.6.26?
Physaddr in mtd->point()
Waiting on dwmw2
Todo Features
Added compression options (LZO, LZMA, etc)
brd RAM disk support

18. Resources Git tree Sourceforge site
git://git.infradead.org/home/jehulber/axfs.git
Sourceforge site

19. App launch time