CVS log for xfs-linux/xfs_mru_cache.h

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Default branch: MAIN
Current tag: MAIN

Revision 1.2 / (download) - annotate - [select for diffs], Thu Aug 2 15:55:15 2007 UTC (10 years, 2 months ago) by dgc.longdrop.melbourne.sgi.com
Branch: MAIN
CVS Tags: HEAD
Changes since 1.1: +2 -4 lines
Diff to previous 1.1 (colored)

On-demand reaping of the MRU cache

Instead of running the mru cache reaper all the time based on a
timeout, we should only run it when the cache has active objects.
This allows CPUs to sleep when there is no activity rather than
be woken repeatedly just to check if there is anything to do.
Merge of xfs-linux-melb:xfs-kern:29305a by kenmcd.

  Change the reaper to start when the first object is stored
  in the cache and stop when the last object is reaped.

Revision 1.1 / (download) - annotate - [select for diffs], Mon Jul 9 06:12:03 2007 UTC (10 years, 3 months ago) by dgc.longdrop.melbourne.sgi.com
Branch: MAIN

Concurrent Multi-File Data Streams

In media spaces, video is often stored in a frame-per-file format.
When dealing with uncompressed realtime HD video streams in this format,
it is crucial that files do not get fragmented and that multiple files
a placed contiguously on disk.

When multiple streams are being ingested and played out at the same
time, it is critical that the filesystem does not cross the streams
and interleave them together as this creates seek and readahead
cache miss latency and prevents both ingest and playout from meeting
frame rate targets.

This patch set creates a "stream of files" concept into the allocator
to place all the data from a single stream contiguously on disk so
that RAID array readahead can be used effectively. Each additional
stream gets placed in different allocation groups within the
filesystem, thereby ensuring that we don't cross any streams. When
an AG fills up, we select a new AG for the stream that is not in
use.

The core of the functionality is the stream tracking - each inode
that we create in a directory needs to be associated with the
directories' stream. Hence every time we create a file, we look up
the directories' stream object and associate the new file with that
object.

Once we have a stream object for a file, we use the AG that the
stream object point to for allocations. If we can't allocate in that
AG (e.g. it is full) we move the entire stream to another AG. Other
inodes in the same stream are moved to the new AG on their next
allocation (i.e. lazy update).

Stream objects are kept in a cache and hold a reference on the
inode. Hence the inode cannot be reclaimed while there is an
outstanding stream reference. This means that on unlink we need to
remove the stream association and we also need to flush all the
associations on certain events that want to reclaim all unreferenced
inodes (e.g.  filesystem freeze).
Merge of xfs-linux-melb:xfs-kern:29096a by kenmcd.

  Concurrent Multi-File Data Streams feature check in.

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