[JFFS2] why use a very low-efficient method to check all the uncheked inode in garbage_collect_pass
zhengjun
zhengun23 at 126.com
Sat Jun 29 07:53:14 EDT 2013
I encountered a problem with my linux system(uses jffs2 file system)
After scan all inode on the flash, a background thread ( garbage_collect_thread) is start。 Before collecting,
it begins with checking crc of all inodes in inode_cache_list. But unluckly the checking work cost all most 3
minutes。It costs the 98% of all cpu resource.
I found that the time is wasted on finding out the valid inode_cache with specified inode id (c->checked_ino)。
checked_ino is counted from zero to c->higest_ino。
In my system, there are 3000 files,but with higest_ino reached to 27262976。
(Because the old file is replaced by new file, by first delete then copy)。
So the most of time, jffs2_get_inode_cache can not find a valid inode with c->checked_ino。
So the useless search works wastes a lot of time.
why?
why use a increased index to find each indoe_cache in inode_cache_list, but you never know which index is the valide ino.
The indode_cache_list is a hash table.
why not use a deep-first-search method to get each inode in hash table?
Just remember next valid ino in c->checked_ino.
Now I designed a new search method。 It works much more efficiently.
Could you optimize these code for better work? Thanks!
jffs2_garbage_collect_pass()
{
....
if( c->unchecked_size )
{
ic = jffs2_get_inode_cache_next( c, & c->checked_ino ); // new search method
if( !ic )
{
BUG();
}
}
....
}
struct jffs2_inode_cache * jffs2_get_inode_cache_next( struct jffs2_sb_info * c, uint32_t * ino )
{
struct jffs2_inode_cache * ret;
uint32_t curIno;
uint32_t ihash;
curIno = *ino;
ihash = curino % 128;
ret = c->inode_cache_list[ihash];
while( NULL != ret )
{
if( ret->ino >= curInfo )
{
goto findinode;
}
ret = ret ->next;
}
for( ihash = ihash + 1; ihash < 128; ihash ++ )
{
if( NULL != ( ret = c->inode_cache_list[ihash] ) )
goto findinode;
}
return NULL;
findinode:
if( ret->next )
{
*ino = ret->next->ino;
} else
{
*ino = ihash + 1;
}
return ret;
}
More information about the linux-mtd
mailing list