| Message ID | cover.1684967923.git.dsterba@suse.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Parameter cleanups in extent state helpers | expand |
On 2023/5/25 07:04, David Sterba wrote: > This is motivated by the gfp parameter passed to all the helpers and how > to get rid of it. Most of the values are GFP_NOFS with some exceptions. > One of them (GFP_NOFAIL) can be removed the other one (GFP_NOWAIT) is > transformed to existing parameters. The patchset gives me some inspiration on a wild idea to completely remove the memory allocation inside set/clear_bits(). The core idea is to change extent io tree to have "hole" extent_state, so that every set/clear_bits() call will only need to allocate 2 new extent states, thus we can pre-allocate them. Currently the extent io tree behaves much like no-hole, we only insert new extent_state if there is any bit set for a certain range. Thus the following case will need as many new extent states as the holes: |<------- Range to set bits ------------->| |///| |////| |////| .... |/////| ^ ^ ^ | | \- hole N hole 1 hole 2 But if we keep hole state extents, the above case will only need to allocate 0 new extent state: |<------- Range to set bits ------------->| |///|000|////|0000|////| .... 0000|/////| Although we may still need to allocate up to 2 new extent states even with hole states. The most straightforward example is: |<- Range to clear bits ---->| |//////////////////////////////////////////| But this greatly limits the new allocation needed, thus can make the set/clear_bits() to return void and avoid memory allocation at all (all pre-allocated by callers). Obviously there would be no free lunch, the overall memory usage would increase, especially for fragmented extent io tree. Thus I'm not sure if the hole extent state idea is really a good idea or the existing NOWAIT/NOFAIL allocation is more acceptable... Thanks, Qu > > Module code size is lower for the whole series and stack is reduced in > about 50 functions by 8 bytes. > > David Sterba (9): > btrfs: open code set_extent_defrag > btrfs: open code set_extent_delalloc > btrfs: open code set_extent_new > btrfs: open code set_extent_dirty > btrfs: open code set_extent_bits_nowait > btrfs: open code set_extent_bits > btrfs: drop NOFAIL from set_extent_bit allocation masks > btrfs: pass NOWAIT for set/clear extent bits as another bit > btrfs: drop gfp from parameter extent state helpers > > fs/btrfs/block-group.c | 6 ++-- > fs/btrfs/defrag.c | 3 +- > fs/btrfs/dev-replace.c | 4 +-- > fs/btrfs/extent-io-tree.c | 37 ++++++++++++------- > fs/btrfs/extent-io-tree.h | 62 ++++++++------------------------ > fs/btrfs/extent-tree.c | 27 +++++++------- > fs/btrfs/extent_io.c | 3 +- > fs/btrfs/extent_map.c | 10 +++--- > fs/btrfs/file-item.c | 10 +++--- > fs/btrfs/inode.c | 9 +++-- > fs/btrfs/relocation.c | 10 +++--- > fs/btrfs/tests/extent-io-tests.c | 16 ++++----- > fs/btrfs/zoned.c | 4 +-- > 13 files changed, 91 insertions(+), 110 deletions(-) >