From: Gautham Ananthakrishna <gautham.ananthakrishna@oracle.com>
To: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org
Cc: viro@zeniv.linux.org.uk, matthew.wilcox@oracle.com,
khlebnikov@yandex-team.ru, gautham.ananthakrishna@oracle.com
Subject: [PATCH RFC 2/6] fsnotify: stop walking child dentries if remaining tail is negative
Date: Thu, 21 Jan 2021 18:49:41 +0530 [thread overview]
Message-ID: <1611235185-1685-3-git-send-email-gautham.ananthakrishna@oracle.com> (raw)
In-Reply-To: <1611235185-1685-1-git-send-email-gautham.ananthakrishna@oracle.com>
From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
When notification starts/stops listening events from inode's children it
have to update dentry->d_flags of all positive child dentries. Scanning
may took a long time if directory has a lot of negative child dentries.
This is main beneficiary of sweeping cached negative dentries to the end.
Before patch:
nr_dentry = 24172597 24.2M
nr_buckets = 8388608 2.9 avg
nr_unused = 24158110 99.9%
nr_negative = 24142810 99.9%
inotify time: 0.507182 seconds
After patch:
nr_dentry = 24562747 24.6M
nr_buckets = 8388608 2.9 avg
nr_unused = 24548714 99.9%
nr_negative = 24543867 99.9%
inotify time: 0.000010 seconds
Negative dentries no longer slow down inotify op at parent directory.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Gautham Ananthakrishna <gautham.ananthakrishna@oracle.com>
---
fs/notify/fsnotify.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index 8d3ad5e..4ccb59d 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -127,8 +127,12 @@ void __fsnotify_update_child_dentry_flags(struct inode *inode)
* original inode) */
spin_lock(&alias->d_lock);
list_for_each_entry(child, &alias->d_subdirs, d_child) {
- if (!child->d_inode)
+ if (!child->d_inode) {
+ /* all remaining children are negative */
+ if (d_is_tail_negative(child))
+ break;
continue;
+ }
spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
if (watched)
--
1.8.3.1
next prev parent reply other threads:[~2021-01-21 15:31 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-21 13:19 [PATCH RFC 0/6] fix the negative dentres bloating system memory usage Gautham Ananthakrishna
2021-01-21 13:19 ` [PATCH RFC 1/6] dcache: sweep cached negative dentries to the end of list of siblings Gautham Ananthakrishna
2021-04-14 3:00 ` Al Viro
2021-04-15 16:50 ` Al Viro
2021-04-14 3:41 ` Al Viro
2021-04-15 16:25 ` Al Viro
2021-01-21 13:19 ` Gautham Ananthakrishna [this message]
2021-01-21 13:19 ` [PATCH RFC 3/6] dcache: add action D_WALK_SKIP_SIBLINGS to d_walk() Gautham Ananthakrishna
2021-01-21 13:19 ` [PATCH RFC 4/6] dcache: stop walking siblings if remaining dentries all negative Gautham Ananthakrishna
2021-01-21 13:19 ` [PATCH RFC 5/6] dcache: push releasing dentry lock into sweep_negative Gautham Ananthakrishna
2021-01-21 13:19 ` [PATCH RFC 6/6] dcache: prevent flooding with negative dentries Gautham Ananthakrishna
2021-04-14 3:56 ` Al Viro
2021-03-31 14:23 ` [PATCH RFC 0/6] fix the negative dentres bloating system memory usage Matthew Wilcox
2021-04-14 2:40 ` Al Viro
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