diff options
| -rw-r--r-- | ext2fs-fosdem2005.mgp | 67 |
1 files changed, 34 insertions, 33 deletions
diff --git a/ext2fs-fosdem2005.mgp b/ext2fs-fosdem2005.mgp index d829f7ca..27b5077c 100644 --- a/ext2fs-fosdem2005.mgp +++ b/ext2fs-fosdem2005.mgp @@ -1,7 +1,7 @@ +# "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 @@ -9,20 +9,23 @@ -Supporting Larger File Systems in the Hurd - +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 @@ -35,7 +38,6 @@ Need for supporting larger file systems 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 @@ -46,33 +48,31 @@ Timeline User pager in GNU Mach -(xfig missing) Address space - ^ m_o_d_supply v m_o_d_return (Mach API, mapping) - Memory object - ^ pager_read_page v pager_write_page (libpager API, association) - User-supplied backstore + 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 -(xfig missing) - Address space region (image) - Whole store (partition) + Memory mapping of the whole store Applies only for metadata! - bptr (block -> buffer) + 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 1) +Patched ext2fs, part one -(xfig missing) Address space region mapping Array of buffers @@ -81,16 +81,18 @@ Patched ext2fs (Part 1) Association of buffers changes (reassocation) - It's important reassociation to occur only with buffers not in core + It's important reassociation to occur on buffers that are not in core %page -Patched ext2fs (Part 2) +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) @@ -103,35 +105,39 @@ Patched ext2fs (Part 2) When unassociated block is requested + %font "typewriter", size 4, cont retry: - i=hint; + i = hint; while (buffers[i] is referenced or in core) { i = (i + 1) % nbuffers; if (i == hint) { - return_unreferenced_buffers(); + return_unreferenced_buffers (); goto retry; + } } hint = i + 1; - deassociate(buffers[i]); - associate(buffers[i],block); + deassociate (buffers[i]); + associate (buffers[i], block); return buffers[i]; %page -Necessity for Notification +Notification for evicted pages - Notification is essential for reassociation + 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 -libpager optimization +Pager optimization 1. Mach returns page to pager without leaving it in core @@ -139,7 +145,7 @@ libpager optimization 3. User task touches the page -4. Mach requests the same page from libpager +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 @@ -148,15 +154,10 @@ libpager optimization 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: |