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Diffstat (limited to 'hurd/translator/ext2fs/ogi-fosdem2005.mgp')
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diff --git a/hurd/translator/ext2fs/ogi-fosdem2005.mgp b/hurd/translator/ext2fs/ogi-fosdem2005.mgp deleted file mode 100644 index 27b5077c..00000000 --- a/hurd/translator/ext2fs/ogi-fosdem2005.mgp +++ /dev/null @@ -1,165 +0,0 @@ -# "Supporting Larger ext2 File Systems in the Hurd" -# Written by Ognyan Kulev for presentation at FOSDEM 2005. -# Content of this file is in public domain. -%include "default.mgp" -%page -%nodefault -%center, font "thick", size 5 - - - - -Supporting Larger ext2 File Systems in the Hurd - - - -%font "standard", size 4 -Ognyan Kulev -%size 3 -<ogi@fmi.uni-sofia.bg> - - -%size 4 -FOSDEM 2005 - -%page - -Need for supporting larger file systems - - Active development during 1995-1997 - - Hurd 0.2 was released in 1997 and it was very buggy - - Many bugs are fixed since then - - The 2G limit for ext2 file systems becomes more and more annoying - -%page - -Timeline - - 2002: Time for graduating, fixing the 2G limit in Hurd's ext2fs and implementing ext3fs were chosen for MSc thesis - - 2003: First alfa quality patch - - 2004: Graduation, ext2fs patch in Debian, but ext3fs is unstable - -%page - -User pager in GNU Mach - - Address space - memory_object_data_supply - memory_object_data_return - Memory object (Mach concept) - pager_read_page - pager_write_page - User-supplied backstore (libpager concept) - -%page - -Current ext2fs - - Memory mapping of the whole store - - Applies only for metadata! - - bptr (block -> data pointer) - = image pointer + block * block_size - - Inode and group descriptor tables are used as if they are continous in memory - -%page - -Patched ext2fs, part one - - Address space region - mapping - Array of buffers - association - Store - - Association of buffers changes (reassocation) - - It's important reassociation to occur on buffers that are not in core - -%page - -Patched ext2fs, part two - - Always use buffer guarded by - disk_cache_block_ref (block -> buffer) - disk_cache_block_deref (release buffer) - - Buffer = data + reference count + flags (e.g. INCORE) - - Calling some functions implies releasing buffer: - pokel_add (pokels are list of dirty buffers) - record_global_poke (use pokel_add) - sync_global_ptr (sync immediately) - record_indir_poke (use pokel_add) - - Use ihash for mapping block to buffer - -%page - -When unassociated block is requested - - -%font "typewriter", size 4, cont -retry: - i = hint; - while (buffers[i] is referenced or in core) { - i = (i + 1) % nbuffers; - if (i == hint) { - return_unreferenced_buffers (); - goto retry; - } - } - hint = i + 1; - - deassociate (buffers[i]); - associate (buffers[i], block); - - return buffers[i]; - -%page - -Notification for evicted pages - - Notification is essential for optimal reassociation - - Precious pages in Mach - - Slight change to API and ABI of libpager is required - - Mach sometimes doesn't notify! - -%page - -Pager optimization - -1. Mach returns page to pager without leaving it in core - -2. Pager becomes unlocked because of calling callback pager_write_page - -3. User task touches the page - -4. Mach requests the same page from pager - -5. XXX Pager supplies the page that was returned by Mach, instead of calling callback pager_read_page - -%page - -Future directions - - Committing in the Hurd :-) - Block sizes of 1K and 2K - Run-time option for buffer array size (?) - Compile-time option for memory-mapping the whole store - Upgrade of UFS - Extended attributes (EAs) and Access control lists (ACLs) - -# Local Variables: -# mgp-options: "-g 640x480" -# End: |