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 <guochun...@vivo.com> --- v1: https://lore.kernel.org/linux-erofs/588351c0-93f9-4a04-a923-15aae8b71...@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 | 59 +++++++++++++++++++++++++++++++++--------------- 1 file changed, 41 insertions(+), 18 deletions(-) diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c index 4558e6a98336..1a7f56259f45 100644 --- a/fs/erofs/zdata.c +++ b/fs/erofs/zdata.c @@ -896,14 +896,11 @@ 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_prepare_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 @@ -911,7 +908,7 @@ 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 @@ -920,8 +917,18 @@ 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 = false; + + /* Using trylock to avoid deadlock with z_erofs_put_pcluster() */ + if (!spin_trylock(&pcl->lockref.lock)) + return free; + free = erofs_prepare_to_release_pcluster(sbi, pcl); spin_unlock(&pcl->lockref.lock); if (free) { atomic_long_dec(&erofs_global_shrink_cnt); @@ -953,16 +960,27 @@ 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_lock(&sbi->managed_pslots); + free = erofs_prepare_to_release_pcluster(sbi, pcl); + xa_unlock(&sbi->managed_pslots); + } + if (!free) + atomic_long_inc(&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) @@ -983,7 +1001,7 @@ 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; } @@ -1285,6 +1303,7 @@ 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; @@ -1343,8 +1362,10 @@ 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); } @@ -1390,6 +1411,12 @@ 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; } @@ -1412,10 +1439,6 @@ 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; } -- 2.25.1
