[v2,0/8] Minor cleanups and improvements to swap freeing code

Message

Kemeng Shi March 18, 2025, 3:06 p.m. UTC

v1->v2:
-Collect RVB from Tim
-Drop patch to factor out __swap_entry_free()
-Improve changelog and add more comment.
-Avoid unneeded lock re-aquire

Hi All,
This series contains some cleanups and improvements which are made
during learning swapfile. Here is a summary of the changes:
1. Function nameing improvments.
-Use "put" instead of "free" to name functions which only do actual free
when count drops to zero.
-Use "entry" to name function only frees one swap slot. Use "entries" to
name function could may free multi swap slots within one cluster. Use
"_nr" suffix to name function which could free multi swap slots spanning
cross multi clusters.
2. Eliminate the need to set swap slot to intermediate SWAP_HAS_CACHE
value before do actual free by using swap_entry_range_free()
3. Add helpers swap_entries_put_map() and swap_entries_put_cache() as a
general-purpose routine to free swap entries within a single cluster
which will try batch-remove first and fallback to put eatch entry
indvidually with cluster lock acquired/released only once. By using 
these helpers, we could remove repeated code, levarage batch-remove in
more cases and aoivd to acquire/release cluster lock for each single
swap entry.

Kemeng Shi (8):
  mm: swap: rename __swap_[entry/entries]_free[_locked] to
    swap_[entry/entries]_put[_locked]
  mm: swap: remove unneeded VM_BUG_ON(*map != SWAP_HAS_CACHE) in
    swap_entry_range_free()
  mm: swap: use swap_entries_free() to free swap entry in
    swap_entry_put_locked()
  mm: swap: use swap_entries_free() drop last ref count in
    swap_entries_put_nr()
  mm: swap: drop last SWAP_MAP_SHMEM flag in batch in
    swap_entries_put_nr()
  mm: swap: free each cluster individually in swap_entries_put_map_nr()
  mm: swap: factor out helper to drop cache of entries within a single
    cluster
  mm: swap: replace cluster_swap_free_nr() with
    swap_entries_put_[map/cache]()

 mm/swapfile.c | 157 ++++++++++++++++++++++++--------------------------
 1 file changed, 75 insertions(+), 82 deletions(-)

Comments

Tim Chen March 18, 2025, 5:03 p.m. UTC | #1

On Tue, 2025-03-18 at 23:06 +0800, Kemeng Shi wrote:
> v1->v2:
> -Collect RVB from Tim
> -Drop patch to factor out __swap_entry_free()
> -Improve changelog and add more comment.
> -Avoid unneeded lock re-aquire
> 

The updated patch series look good to me.  You can add

Reviewed-by: Tim Chen <[e-mail]>

for the series.


Tim