Otellini Keynote Highlights

							         AXFS
Advanced XIP Filing System
       Jared Hulbert
         Numonyx
       April 15, 2008
     Agenda
•Goal/History
•Features
•Architecture
•Test Results
•Kernel Integration
    Project Goals
Supportable solution for
 application XIP
Fine grained control on
 compression
Flexible use of all system
 memories
 –NOR, NAND, RAM
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
  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
            Features
Basic       –Read-only
Attribute   –64bit
            –Designed with CE requirements in
s           mind

Compressi   –4KB-4GB compression block size
on          –Page by page uncompression map for
            XIP

Flexible    –MTD (NAND/NOR)
Mount       –block device
            –split across XIP NOR and non-XIP
            NAND

Tools       –GPL mkfs.axfs
            –Supported propriety image builder
            available
     Onmedia Format
   Super Block          Superblock
   Region Descriptor      – Points to many
                            region
   Region Descriptor        descriptor
   Region Descriptor    Region
                         Descriptor
    File Info             – Describes /
                            points to one
                            region
   XIP Region
                        Regions
                          – Each data type
Compressed Region           / table has
                            own region
                          – permissions,
    Data                           inode

    Flow Node Index                        Node Type Table


XIP Region
                             XIP   Compressed
  Index 0                                                        cblock Offset Table

  Index 1
                                                                 Compressed Region
                             cnode Offset Table
  Index 2

                 Uncompressed cblock
                   Index 0   Index 1    Index 2   Index 3


            Application Virtual Pages
             Index 1                                   Index 3
             Mount Options
mount –t axfs –o block_dev=/dev/mtd1 /dev/mtd0 /mnt/axfs

 /dev/sda0   ~/file.axfs   /dev/mtd0   /dev/mtd0   /dev/mtd0
             (-o loop)       (NAND)      (NOR)       (NOR)

                                                    AXFS
                                                    Image
                                        AXFS        Part 1
  AXFS         AXFS         AXFS
                                        Image      (MMAP)
  Image        Image        Image

                                                   /dev/mtd1
                                                    (NAND)

                                                    AXFS
                                                    Image
                                                    Part 2
                                                     (IO)
  Image Size Comparison
CRAMFS(XIP)

  AXFS(XIP)

       JFFS2

    CRAMFS

   Squashfs

        AXFS

               0                16              32   48
                                           MB

~1 year old Opie build from OpenEmbedded
    Total Memory Used

   JFFS2



SquashFS



   AXFS


           0   32        64                       96
                    MB        Rootfs size   RAM used
Fitting into Real Chips

    JFFS2




 SquashFS




    AXFS


            0   32        64                            96
                     MB        Rootfs size   RAM used
  Performance: direct
      comparison
 PXA270         – 520 MHz (CPU)
                 – 208 MHz (memory clock)
                 – 104 MHz (SDRAM bus)
                 – 52 MHz (NOR flash bus)

                 – xipImage
 Linux-2.6.22   – CONFIG_PREEMPT=y
                 – MTD updated to Sept 25 git
                   pull
                 – “mem=24MB” in kernel
                   commandline
 Opie build
                 – OpenEmbedded
                 – ~1 year old
    Performance: Direct
        Comparison




Root Filing System Comparison Video at:
http://www.youtube.com/watch?v=fu6Yj7iK
 EiA
 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
 – data in NAND
 “SnD”
 – code in CRAMFS from NAND
 – data on NAND
Performance: realistic
      comparison




XIP vs. SND: Realistic Performance Comparison Video
 at:
http://www.youtube.com/watch?v=HUqFrA4FYd0
    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
            Resources

Git tree
 git://git.infradead.org/home/jehulber
  /axfs.git


Sourceforge site
 http://axfs.sf.net
                        App launch time
           200

           175

           150

           125
Time (s)




           100

            75

            50

            25

             0
                 AXFS   JFFS2       CRAMFS       SquashFS        AXFS        JFFS2      CRAMFS   SquashFS
                          24MB of RAM                                          32MB of RAM

                                Shuttle Video Launch Time (s)   PDF Reader Launch Time (s)
                                Webbrowser Launch Time (s)      SDL Quake Launch Time (s)