The patch titled
Subject: zram: free slot memory early during write
has been added to the -mm mm-unstable branch. Its filename is
zram-free-slot-memory-early-during-write.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zram-free-slot-memory-early-during-write.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Subject: zram: free slot memory early during write
Date: Tue, 10 Dec 2024 19:53:56 +0900
In the current implementation entry's previously allocated memory is
released in the very last moment, when we already have allocated a new
memory for new data. This, basically, temporarily increases memory usage
for no good reason. For example, consider the case when both old (stale)
and new entry data are incompressible so such entry will temporarily use
two physical pages - one for stale (old) data and one for new data. We
can release old memory as soon as we get a write request for entry.
Link: https://lkml.kernel.org/r/20241210105420.1888790-3-senozhatsky@xxxxxxxxxxxx
Signed-off-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/block/zram/zram_drv.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
--- a/drivers/block/zram/zram_drv.c~zram-free-slot-memory-early-during-write
+++ a/drivers/block/zram/zram_drv.c
@@ -1651,6 +1651,11 @@ static int zram_write_page(struct zram *
unsigned long element = 0;
enum zram_pageflags flags = 0;
+ /* First, free memory allocated to this slot (if any) */
+ zram_slot_lock(zram, index);
+ zram_free_page(zram, index);
+ zram_slot_unlock(zram, index);
+
mem = kmap_local_page(page);
if (page_same_filled(mem, &element)) {
kunmap_local(mem);
@@ -1746,13 +1751,7 @@ compress_again:
zs_unmap_object(zram->mem_pool, handle);
atomic64_add(comp_len, &zram->stats.compr_data_size);
out:
- /*
- * Free memory associated with this sector
- * before overwriting unused sectors.
- */
zram_slot_lock(zram, index);
- zram_free_page(zram, index);
-
if (comp_len == PAGE_SIZE) {
zram_set_flag(zram, index, ZRAM_HUGE);
atomic64_inc(&zram->stats.huge_pages);
_
Patches currently in -mm which might be from senozhatsky@xxxxxxxxxxxx are
zram-panic-when-use-ext4-over-zram-fix.patch
zram-cond_resched-in-writeback-loop.patch
zram-free-slot-memory-early-during-write.patch
zram-remove-entry-element-member.patch
zram-factor-out-zram_same-write.patch
zram-factor-out-zram_huge-write.patch
zram-factor-out-different-page-types-read.patch
