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Date: Wed, 18 Jun 2008 22:43:25 +0800
From: "Bob Zhang" <zhanglinbao@...il.com>
To: "Jared Hulbert" <jaredeh@...il.com>
Cc: linux-kernel@...r.kernel.org
Subject: Re: Does anyone run AXFS in 2.4 version of kernel ? I am trying my best to apply AXFS patches into 2.4.18
Good news , AXFS XIP has already worked well in 2.4.21 kernel .
Till now , in 2.4.21 , AXFS compressed and XIP both work well.
it can be said that balanced XIP is OK.
all files related with AXFS have been ported to 2.4.21 kernel .
My rootfs is a simple file system consisted fo busybox .
I have set most pages data of /bin/busybox to be XIP and some pages of
/bin/busybox are set to be compressed , and /strace is no XIP ,full
compressed .
I will execute ifconfig(linked to busybox) and strace to keep them distinct .
1 , Preparation
In fact , the information from profiling data is engough to create a
Input xml file .
Through reading the source code of mkfs.axfs.c ( source code of
generating the axfs img ) , I know that.
in 2.4.21 kernel , our profiling data is like this : complete file can
be found at attachement named "axfs_profiling_data.txt"
<<axfs_profiling_data.txt>>
/ $ cat /proc/axfs/volume0
#filename offset refer_count
you can put the offset into xml file needed by mkfs.axfs.c
./bin/busybox,0,7
./bin/busybox,28672,2
./bin/busybox,53248,4
./bin/busybox,143360,1
./bin/busybox,147456,1
./bin/busybox,151552,6
./bin/busybox,155648,9
./bin/busybox,159744,4
./bin/busybox,163840,7
./bin/busybox,167936,4
./bin/busybox,204800,3
./bin/busybox,233472,2
./bin/busybox,237568,2
./bin/busybox,241664,2
./bin/busybox,245760,2
./bin/busybox,249856,2
so our Input file is like this , complete file can be found at
attachment "axfs.xml" <<axfs.xml>>
Note : the size is all "4096".
<xipfsmap>
<file>
<name>./bin/busybox</name>
<chunk>
<size>4096</size>
<offset>0</offset>
</chunk>
<chunk>
<size>4096</size>
<offset>28672</offset>
</chunk>
<chunk>
<size>4096</size>
<offset>53248</offset>
</chunk>
.....
</xipfsmap>
Note: in fact <size>? </size> , must it be 4096 ? Certainly not , if
you find some contiguous pages are called frequently , for example ,
0~8191
you can write it like this:
<chunk>
<size>8192</size>
<offset> 0 </offset>
</chunk>
Create a new partially XIP rootfs image .
mkfs.axfs -i axfs.xml root_fs balanced_xip.img
Detailed log can be found at attachment named "create_xip_image.log"
<<create_xip_image.log>>
because of debugging info added by me , so you only need to pay
attention to such words
"set_page_stat"
"node_type = XIP"
"node_index[375] = 7"
number of files: 325
number of 4KB nodes: 648
number of 4KB xip nodes: 39 //XIP pages number . you
can how many "chunk" items in the xml file
number of xip files: 1 // because I
only set some pages of /bin/busybox to XIP, no setting other files .
2, testing and verifying
At last , my kernel-2.4.21 with axfs 's booting info is like this ,
complete file can be found at attachment named xip_booting.txt
<<xip_booting.txt>>
because I added debug info , so booting messages is too large .
but you only need to pay attention to such words
<< --------- Reading XIP page ------------ >>
/// --------- Reading Compressed page ------------ ///
node_type = XIP
node_type = Compressed
For diffent kind of pages , kernel will call respective routines to handle.
XIP page: axfs_file_read->xip_file_read->axfs_get_xip_page()
Compressed Page: axfs_file_read->generic_file_read->axfs_readpage
static struct address_space_operations axfs_aops = {
.readpage = axfs_readpage, //for compressed page
.get_xip_page = axfs_get_xip_page, //specially for XIP page reading
};
>From source code :
node_type = AXFS_GET_NODE_TYPE(sbi->metadata, array_index);
bkdmsg("node_type = %s\n",node_type == Compressed?"Compressed":
node_type ==
Byte_Aligned?"Byte_Aligned":
node_type ==
XIP?"XIP":"No this type");
if (AXFS_GET_NODE_TYPE(sbi->metadata, array_index) == XIP) {
printk("\n\n << --------- Reading XIP page
------------ >> \n");
size_read = xip_file_read(filp, buf, readlength, ppos);
} else { //for compressed and Byte_Aligned
printk("\n\n \/\/\/ --------- Reading
Compressed page ------------ \/\/\/ \n");
size_read =
//do_sync_read(filp, buf, readlength,
ppos); //bob modify it
generic_file_read(filp, buf, readlength,
ppos); //2.4 don't support AIO
}
for example ,
when you execute the command "ifconfig" , you will see output like this :
Test Case 1:
/ $ ifconfig ( ifconfig is linked to /bin/busybox , I have set
parts of pages of busybox to XIP , some pages are of Compressed)
in sys_execve() , filename=/proc/self/exe
File:[exec.c], at line:[412], [kernel_read()] will call
file->f_op->read() function
File:[axfs_inode.c], at line:[815], [axfs_file_read()]
axfs_inode_number = 20
File:[axfs_inode.c], at line:[818], [axfs_file_read()] array_index=336
File:[axfs_inode.c], at line:[828], [axfs_file_read()] node_type = XIP
<< --------- Reading XIP page ------------ >>
File:[filemap_xip.c], at line:[134], [xip_file_read()]
File:[filemap_xip.c], at line:[69], [do_xip_mapping_read()] calling
get_xip_page() function pointer
File:[axfs_inode.c], at line:[996], [axfs_get_xip_page()]
File:[axfs_inode.c], at line:[1000], [axfs_get_xip_page()]
axfs_get_xip_page:based on
axfs_inode_number:(20)array_index=(1443109011456)
File:[axfs_inode.c], at line:[1002], [axfs_get_xip_page()]
axfs_get_xip_page:array_index=336
File:[exec.c], at line:[920], [do_execve()] retval of prepare_binprm() = 128
File:[exec.c], at line:[925], [do_execve()] retval of
copy_strings_kernel() = 0
File:[exec.c], at line:[935], [do_execve()] retval of copy_strings 2 = 0
File:[exec.c], at line:[412], [kernel_read()] will call
file->f_op->read() function
File:[axfs_inode.c], at line:[815], [axfs_file_read()]
axfs_inode_number = 20
File:[axfs_inode.c], at line:[818], [axfs_file_read()] array_index=336
File:[axfs_inode.c], at line:[828], [axfs_file_read()] node_type = XIP
<< --------- Reading XIP page ------------ >>
File:[filemap_xip.c], at line:[134], [xip_file_read()]
File:[filemap_xip.c], at line:[69], [do_xip_mapping_read()] calling
get_xip_page() function pointer
File:[axfs_inode.c], at line:[996], [axfs_get_xip_page()]
File:[axfs_inode.c], at line:[1000], [axfs_get_xip_page()]
axfs_get_xip_page:based on
axfs_inode_number:(20)array_index=(1443109011456)
File:[axfs_inode.c], at line:[1002], [axfs_get_xip_page()]
axfs_get_xip_page:array_index=336
File:[axfs_inode.c], at line:[476], [axfs_mmap()]
bob:file->f_mapping address = c0199734
File:[axfs_inode.c], at line:[477], [axfs_mmap()]
bob:file->f_mapping address->a_ops = c00e5e58
File:[binfmt_elf.c], at line:[752], [load_elf_binary()] bob
commentted padzero(elf_bss)
File:[exec.c], at line:[940], [do_execve()] retval of
search_binary_handler() = 0
File:[sys_arm.c], at line:[273], [sys_execve()] do_execve return 0
ifconfig: no usable address families found
ifconfig: socket: Address family not supported by protocol
Test Case 2: (fully Compressed pages ,no XIP,you will see no
./strace in axfs.xml)
/ $ ./strace -h
/ $
/ $ ./strace
in sys_execve() , filename=./strace
File:[exec.c], at line:[412], [kernel_read()] will call
file->f_op->read() function
File:[axfs_inode.c], at line:[815], [axfs_file_read()]
axfs_inode_number = 13
File:[axfs_inode.c], at line:[818], [axfs_file_read()] array_index=107
File:[axfs_inode.c], at line:[828], [axfs_file_read()] node_type =
Compressed
/// --------- Reading Compressed page ------------ ///
File:[exec.c], at line:[920], [do_execve()] retval of prepare_binprm() = 128
File:[exec.c], at line:[925], [do_execve()] retval of
copy_strings_kernel() = 0
File:[exec.c], at line:[935], [do_execve()] retval of copy_strings 2 = 0
File:[exec.c], at line:[412], [kernel_read()] will call
file->f_op->read() function
File:[axfs_inode.c], at line:[815], [axfs_file_read()]
axfs_inode_number = 13
File:[axfs_inode.c], at line:[818], [axfs_file_read()] array_index=107
File:[axfs_inode.c], at line:[828], [axfs_file_read()] node_type =
Compressed
/// --------- Reading Compressed page ------------ ///
File:[axfs_inode.c], at line:[476], [axfs_mmap()]
bob:file->f_mapping address = c1f68994
File:[axfs_inode.c], at line:[477], [axfs_mmap()]
bob:file->f_mapping address->a_ops = c00e5e58
File:[binfmt_elf.c], at line:[752], [load_elf_binary()] bob
commentted padzero(elf_bss)
File:[exec.c], at line:[940], [do_execve()] retval of
search_binary_handler() = 0
File:[sys_arm.c], at line:[273], [sys_execve()] do_execve return 0
./strace: -c and -ff are mutually exclusive options
/ $
/ $
Examples above can show that my XIP and compressed both work well.
Best Regards,
Bob
View attachment "axfs.xml" of type "text/xml" (3092 bytes)
View attachment "axfs_profiling_data.txt" of type "text/plain" (1597 bytes)
Download attachment "create_xip_image.log" of type "application/octet-stream" (42316 bytes)
View attachment "xip_booting.txt" of type "text/plain" (36438 bytes)
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