Hi, I have been studying JFS on and off for quite a while. But I can never be as sure as the experts who really work on JFS on a daily basis. So would you please clarify the following points for me:
(1) Dirty metapages are usually marked as nohomeok. But metapages for bitmap seem to be an exception. Why treat bitmap metapage differently? My guess is because of the careful write strategy JFS is using. If so, why working bitmap is updated first during an allocation, while permanent bitmap is updated first during a free? I understand some metapages (control nodes in the disk space map) does not need to be logged because their information can be reconstructued easily. When are they updated normally? (2) The directory index table seems to try to bridge the legacy linear offset and the real cookie in JFS - a leaf node number plus a slot number. What if an entry's location changes after its index is put into the table (e.g., a split of leaf node)? Should there be something like update_index() in addition to add_index() and free_index()? The size of the directoy is the size of the directory index table. The index is persistent because it is never reused. The table must grow forever because freed index is not reused. How is the performance loss due to maintaing such a large table? Maybe we can simply encode the leaf node number and the slot number into one 64-bit cookie. That would get rid of the table. I must miss something? Thanks for your insights. -Zhihui _______________________________________________ Jfs-discussion mailing list [EMAIL PROTECTED] http://www-124.ibm.com/developerworks/oss/mailman/listinfo/jfs-discussion
