On 06/21/2014 12:35 AM, Ivan Shapovalov wrote:
On Saturday 21 June 2014 at 00:39:54, Ivan Shapovalov wrote:
v1: - initial implementation (patches 1, 2)
v2: - cleanup, fixes discovered in debug mode
- saner logging
- assertions
- enablement of discard through mount option
v3: - fixed the extent merge loop in discard_atom()
v4: - squashed fix-ups into the main patch (with exception of reiser4_debug())
- fixed bug in usage of division ops discovered while building on ARM
v5: - squashed mount option into the main patch
- refactor based on discussion (see commit msg)
- splitted off blocknr_list code
- replaced ->discard_set with ->delete_set and ->aux_delete_set
Ivan Shapovalov (4):
reiser4: make space_allocator's check_blocks() reusable.
reiser4: add an implementation of "block lists", splitted off the discard code.
reiser4: add reiser4_debug(): a conditional equivalent of reiser4_log().
reiser4: discard support: initial implementation using linked lists.
fs/reiser4/Makefile | 2 +
fs/reiser4/block_alloc.c | 49 ++---
fs/reiser4/block_alloc.h | 14 +-
fs/reiser4/blocknrlist.c | 315 ++++++++++++++++++++++++++++++
fs/reiser4/debug.h | 4 +
fs/reiser4/dformat.h | 2 +
fs/reiser4/discard.c | 247 +++++++++++++++++++++++
fs/reiser4/discard.h | 31 +++
fs/reiser4/forward.h | 1 +
fs/reiser4/init_super.c | 2 +
fs/reiser4/plugin/space/bitmap.c | 84 +++++---
fs/reiser4/plugin/space/bitmap.h | 2 +-
fs/reiser4/plugin/space/space_allocator.h | 4 +-
fs/reiser4/super.h | 4 +-
fs/reiser4/txnmgr.c | 125 +++++++++++-
fs/reiser4/txnmgr.h | 63 +++++-
fs/reiser4/znode.c | 9 +-
17 files changed, 884 insertions(+), 74 deletions(-)
create mode 100644 fs/reiser4/blocknrlist.c
create mode 100644 fs/reiser4/discard.c
create mode 100644 fs/reiser4/discard.h
Also I would like if this code could be given a review. :)
Great! Looks nice for me, thanks!
There are 2 issues, though...
1) kmalloc/kfree a huge number of 32-byte chunks (blocknr_list entries) is
suboptimal. There is a special low-level memory allocator for such purposes.
Take a look how we initialize so-called "slab cache" for jnodes
(_jnode_slab),
atoms (_atom_slab), etc, and allocate memory for them (kmem_cache_alloc()).
2) A lot of blocknr_list entries are allocated at flush time, when the
high-level
allocator (txmod.c) makes "relocation decisions" (especially when txmod=wa).
The problem is that the flush (with the following commit) usually is the
file system
response to memory pressure notifications, when additional memory allocation
is not desirable.
I think that with the fixed (1) we'll include the discard support (if
everything will
be OK in the next 1-2 weeks).
As to (2): that is a common problem of all Linux subsystems which want
memory
to free memory. It is unresolvable, however, we can improve the
situation. It
would be nice to implement a per-atom pool of memory (as a list of
kmalloc-ed
buffers with "cursors") with an optional possibility to pre-allocate 1-2
such buffers
at atom initialization time. But this is for the future...
I don't see other urgent improvements. Yes, overall scalability of
rb-trees is better,
as we found, however, merging rb-trees is more expensive, plus atom's fusion
is not a background process, so it can lead to performance drop. There are
rb-trees with fingers, however I haven't seen their implementation on C
language
(it can be not so simple).
Thanks!
Edward.
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