The patch titled
Subject: mm: zswap: support exclusive loads
has been added to the -mm mm-unstable branch. Its filename is
mm-zswap-support-exclusive-loads.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-zswap-support-exclusive-loads.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Subject: mm: zswap: support exclusive loads
Date: Wed, 7 Jun 2023 19:51:43 +0000
Commit 71024cb4a0bf ("frontswap: remove frontswap_tmem_exclusive_gets")
removed support for exclusive loads from frontswap as it was not used.
Bring back exclusive loads support to frontswap by adding an "exclusive"
output parameter to frontswap_ops->load.
On the zswap side, add a module parameter to enable/disable exclusive
loads, and a config option to control the boot default value. Refactor
zswap entry invalidation in zswap_frontswap_invalidate_page() into
zswap_invalidate_entry() to reuse it in zswap_frontswap_load() if
exclusive loads are enabled.
With exclusive loads, we avoid having two copies of the same page in
memory (compressed & uncompressed) after faulting it in from zswap. On
the other hand, if the page is to be reclaimed again without being
dirtied, it will be re-compressed. Compression is not usually slow, and a
page that was just faulted in is less likely to be reclaimed again soon.
Link: https://lkml.kernel.org/r/20230607195143.1473802-1-yosryahmed@xxxxxxxxxx
Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Suggested-by: Yu Zhao <yuzhao@xxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Dan Streetman <ddstreet@xxxxxxxx>
Cc: Domenico Cerasuolo <cerasuolodomenico@xxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Nhat Pham <nphamcs@xxxxxxxxx>
Cc: Seth Jennings <sjenning@xxxxxxxxxx>
Cc: Vitaly Wool <vitaly.wool@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/frontswap.h | 2 +-
mm/Kconfig | 16 ++++++++++++++++
mm/frontswap.c | 10 ++++++++--
mm/zswap.c | 28 ++++++++++++++++++++--------
4 files changed, 45 insertions(+), 11 deletions(-)
--- a/include/linux/frontswap.h~mm-zswap-support-exclusive-loads
+++ a/include/linux/frontswap.h
@@ -10,7 +10,7 @@
struct frontswap_ops {
void (*init)(unsigned); /* this swap type was just swapon'ed */
int (*store)(unsigned, pgoff_t, struct page *); /* store a page */
- int (*load)(unsigned, pgoff_t, struct page *); /* load a page */
+ int (*load)(unsigned, pgoff_t, struct page *, bool *); /* load a page */
void (*invalidate_page)(unsigned, pgoff_t); /* page no longer needed */
void (*invalidate_area)(unsigned); /* swap type just swapoff'ed */
};
--- a/mm/frontswap.c~mm-zswap-support-exclusive-loads
+++ a/mm/frontswap.c
@@ -206,6 +206,7 @@ int __frontswap_load(struct page *page)
int type = swp_type(entry);
struct swap_info_struct *sis = swap_info[type];
pgoff_t offset = swp_offset(entry);
+ bool exclusive = false;
VM_BUG_ON(!frontswap_ops);
VM_BUG_ON(!PageLocked(page));
@@ -215,9 +216,14 @@ int __frontswap_load(struct page *page)
return -1;
/* Try loading from each implementation, until one succeeds. */
- ret = frontswap_ops->load(type, offset, page);
- if (ret == 0)
+ ret = frontswap_ops->load(type, offset, page, &exclusive);
+ if (ret == 0) {
inc_frontswap_loads();
+ if (exclusive) {
+ SetPageDirty(page);
+ __frontswap_clear(sis, offset);
+ }
+ }
return ret;
}
--- a/mm/Kconfig~mm-zswap-support-exclusive-loads
+++ a/mm/Kconfig
@@ -46,6 +46,22 @@ config ZSWAP_DEFAULT_ON
The selection made here can be overridden by using the kernel
command line 'zswap.enabled=' option.
+config ZSWAP_EXCLUSIVE_LOADS_DEFAULT_ON
+ bool "Invalidate zswap entries when pages are loaded"
+ depends on ZSWAP
+ help
+ If selected, exclusive loads for zswap will be enabled at boot,
+ otherwise it will be disabled.
+
+ If exclusive loads are enabled, when a page is loaded from zswap,
+ the zswap entry is invalidated at once, as opposed to leaving it
+ in zswap until the swap entry is freed.
+
+ This avoids having two copies of the same page in memory
+ (compressed and uncompressed) after faulting in a page from zswap.
+ The cost is that if the page was never dirtied and needs to be
+ swapped out again, it will be re-compressed.
+
choice
prompt "Default compressor"
depends on ZSWAP
--- a/mm/zswap.c~mm-zswap-support-exclusive-loads
+++ a/mm/zswap.c
@@ -138,6 +138,10 @@ static bool zswap_non_same_filled_pages_
module_param_named(non_same_filled_pages_enabled, zswap_non_same_filled_pages_enabled,
bool, 0644);
+static bool zswap_exclusive_loads_enabled = IS_ENABLED(
+ CONFIG_ZSWAP_EXCLUSIVE_LOADS_DEFAULT_ON);
+module_param_named(exclusive_loads, zswap_exclusive_loads_enabled, bool, 0644);
+
/*********************************
* data structures
**********************************/
@@ -1340,12 +1344,22 @@ shrink:
goto reject;
}
+static void zswap_invalidate_entry(struct zswap_tree *tree,
+ struct zswap_entry *entry)
+{
+ /* remove from rbtree */
+ zswap_rb_erase(&tree->rbroot, entry);
+
+ /* drop the initial reference from entry creation */
+ zswap_entry_put(tree, entry);
+}
+
/*
* returns 0 if the page was successfully decompressed
* return -1 on entry not found or error
*/
static int zswap_frontswap_load(unsigned type, pgoff_t offset,
- struct page *page)
+ struct page *page, bool *exclusive)
{
struct zswap_tree *tree = zswap_trees[type];
struct zswap_entry *entry;
@@ -1415,6 +1429,10 @@ stats:
freeentry:
spin_lock(&tree->lock);
zswap_entry_put(tree, entry);
+ if (!ret && zswap_exclusive_loads_enabled) {
+ zswap_invalidate_entry(tree, entry);
+ *exclusive = true;
+ }
spin_unlock(&tree->lock);
return ret;
@@ -1434,13 +1452,7 @@ static void zswap_frontswap_invalidate_p
spin_unlock(&tree->lock);
return;
}
-
- /* remove from rbtree */
- zswap_rb_erase(&tree->rbroot, entry);
-
- /* drop the initial reference from entry creation */
- zswap_entry_put(tree, entry);
-
+ zswap_invalidate_entry(tree, entry);
spin_unlock(&tree->lock);
}
_
Patches currently in -mm which might be from yosryahmed@xxxxxxxxxx are
memcg-use-seq_buf_do_printk-with-mem_cgroup_print_oom_meminfo.patch
memcg-dump-memorystat-during-cgroup-oom-for-v1.patch
writeback-move-wb_over_bg_thresh-call-outside-lock-section.patch
memcg-flush-stats-non-atomically-in-mem_cgroup_wb_stats.patch
memcg-calculate-root-usage-from-global-state.patch
memcg-remove-mem_cgroup_flush_stats_atomic.patch
cgroup-remove-cgroup_rstat_flush_atomic.patch
mm-zswap-support-exclusive-loads.patch
