[PATCH v4] erofs: free pclusters if no cached folio attached
Chunhai Guo
guochunhai at vivo.com
Mon Nov 11 22:38:42 AEDT 2024
Once a pcluster is fully decompressed and there are no attached cached
folios, its corresponding `struct z_erofs_pcluster` will be freed. This
will significantly reduce the frequency of calls to erofs_shrink_scan()
and the memory allocated for `struct z_erofs_pcluster`.
The tables below show approximately a 96% reduction in the calls to
erofs_shrink_scan() and in the memory allocated for `struct
z_erofs_pcluster` after applying this patch. The results were obtained
by performing a test to copy a 4.1GB partition on ARM64 Android devices
running the 6.6 kernel with an 8-core CPU and 12GB of memory.
1. The reduction in calls to erofs_shrink_scan():
+-----------------+-----------+----------+---------+
| | w/o patch | w/ patch | diff |
+-----------------+-----------+----------+---------+
| Average (times) | 11390 | 390 | -96.57% |
+-----------------+-----------+----------+---------+
2. The reduction in memory released by erofs_shrink_scan():
+-----------------+-----------+----------+---------+
| | w/o patch | w/ patch | diff |
+-----------------+-----------+----------+---------+
| Average (Byte) | 133612656 | 4434552 | -96.68% |
+-----------------+-----------+----------+---------+
Signed-off-by: Chunhai Guo <guochunhai at vivo.com>
---
v3 -> v4:
- modify the patch as Gao Xiang suggested in v3.
v2 -> v3:
- rename erofs_prepare_to_release_pcluster() to __erofs_try_to_release_pcluster()
- use trylock in z_erofs_put_pcluster() instead of erofs_try_to_release_pcluster()
v1: https://lore.kernel.org/linux-erofs/588351c0-93f9-4a04-a923-15aae8b71d49@linux.alibaba.com/
change since v1:
- rebase this patch on "sunset z_erofs_workgroup` series
- remove check on pcl->partial and get rid of `be->try_free`
- update test results base on 6.6 kernel
---
fs/erofs/zdata.c | 54 ++++++++++++++++++++++++++++++++----------------
1 file changed, 36 insertions(+), 18 deletions(-)
diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 6b73a2307460..d2338bd99811 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -885,14 +885,11 @@ static void z_erofs_rcu_callback(struct rcu_head *head)
struct z_erofs_pcluster, rcu));
}
-static bool erofs_try_to_release_pcluster(struct erofs_sb_info *sbi,
+static bool __erofs_try_to_release_pcluster(struct erofs_sb_info *sbi,
struct z_erofs_pcluster *pcl)
{
- int free = false;
-
- spin_lock(&pcl->lockref.lock);
if (pcl->lockref.count)
- goto out;
+ return false;
/*
* Note that all cached folios should be detached before deleted from
@@ -900,7 +897,7 @@ static bool erofs_try_to_release_pcluster(struct erofs_sb_info *sbi,
* orphan old pcluster when the new one is available in the tree.
*/
if (erofs_try_to_free_all_cached_folios(sbi, pcl))
- goto out;
+ return false;
/*
* It's impossible to fail after the pcluster is freezed, but in order
@@ -909,8 +906,16 @@ static bool erofs_try_to_release_pcluster(struct erofs_sb_info *sbi,
DBG_BUGON(__xa_erase(&sbi->managed_pslots, pcl->index) != pcl);
lockref_mark_dead(&pcl->lockref);
- free = true;
-out:
+ return true;
+}
+
+static bool erofs_try_to_release_pcluster(struct erofs_sb_info *sbi,
+ struct z_erofs_pcluster *pcl)
+{
+ bool free;
+
+ spin_lock(&pcl->lockref.lock);
+ free = __erofs_try_to_release_pcluster(sbi, pcl);
spin_unlock(&pcl->lockref.lock);
if (free) {
atomic_long_dec(&erofs_global_shrink_cnt);
@@ -942,16 +947,25 @@ unsigned long z_erofs_shrink_scan(struct erofs_sb_info *sbi,
return freed;
}
-static void z_erofs_put_pcluster(struct z_erofs_pcluster *pcl)
+static void z_erofs_put_pcluster(struct erofs_sb_info *sbi,
+ struct z_erofs_pcluster *pcl, bool try_free)
{
+ bool free = false;
+
if (lockref_put_or_lock(&pcl->lockref))
return;
DBG_BUGON(__lockref_is_dead(&pcl->lockref));
- if (pcl->lockref.count == 1)
- atomic_long_inc(&erofs_global_shrink_cnt);
- --pcl->lockref.count;
+ if (--pcl->lockref.count == 0) {
+ if (try_free && xa_trylock(&sbi->managed_pslots)) {
+ free = __erofs_try_to_release_pcluster(sbi, pcl);
+ xa_unlock(&sbi->managed_pslots);
+ }
+ atomic_long_add(!free, &erofs_global_shrink_cnt);
+ }
spin_unlock(&pcl->lockref.lock);
+ if (free)
+ call_rcu(&pcl->rcu, z_erofs_rcu_callback);
}
static void z_erofs_pcluster_end(struct z_erofs_decompress_frontend *fe)
@@ -972,7 +986,7 @@ static void z_erofs_pcluster_end(struct z_erofs_decompress_frontend *fe)
* any longer if the pcluster isn't hosted by ourselves.
*/
if (fe->mode < Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE)
- z_erofs_put_pcluster(pcl);
+ z_erofs_put_pcluster(EROFS_I_SB(fe->inode), pcl, false);
fe->pcl = NULL;
}
@@ -1274,6 +1288,7 @@ static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be,
int i, j, jtop, err2;
struct page *page;
bool overlapped;
+ bool try_free = true;
mutex_lock(&pcl->lock);
be->nr_pages = PAGE_ALIGN(pcl->length + pcl->pageofs_out) >> PAGE_SHIFT;
@@ -1332,8 +1347,10 @@ static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be,
for (i = 0; i < pclusterpages; ++i) {
page = be->compressed_pages[i];
if (!page ||
- erofs_folio_is_managed(sbi, page_folio(page)))
+ erofs_folio_is_managed(sbi, page_folio(page))) {
+ try_free = false;
continue;
+ }
(void)z_erofs_put_shortlivedpage(be->pagepool, page);
WRITE_ONCE(pcl->compressed_bvecs[i].page, NULL);
}
@@ -1379,6 +1396,11 @@ static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be,
/* pcluster lock MUST be taken before the following line */
WRITE_ONCE(pcl->next, Z_EROFS_PCLUSTER_NIL);
mutex_unlock(&pcl->lock);
+
+ if (z_erofs_is_inline_pcluster(pcl))
+ z_erofs_free_pcluster(pcl);
+ else
+ z_erofs_put_pcluster(sbi, pcl, try_free);
return err;
}
@@ -1401,10 +1423,6 @@ static int z_erofs_decompress_queue(const struct z_erofs_decompressqueue *io,
owned = READ_ONCE(be.pcl->next);
err = z_erofs_decompress_pcluster(&be, err) ?: err;
- if (z_erofs_is_inline_pcluster(be.pcl))
- z_erofs_free_pcluster(be.pcl);
- else
- z_erofs_put_pcluster(be.pcl);
}
return err;
}
--
2.34.1
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