linux-kernel - [PATCH] xfs: optimise xfs_mod

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Date:   Mon, 4 Nov 2019 19:29:40 +0800
From:   Shaokun Zhang <zhangshaokun@...ilicon.com>
To:     <linux-xfs@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     Yang Guo <guoyang2@...wei.com>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Shaokun Zhang <zhangshaokun@...ilicon.com>
Subject: [PATCH] xfs: optimise xfs_mod_icount/ifree when delta < 0

From: Yang Guo <guoyang2@...wei.com>

percpu_counter_compare will be called by xfs_mod_icount/ifree to check
whether the counter less than 0 and it is a expensive function.
let's check it only when delta < 0, it will be good for xfs's performance.

Cc: "Darrick J. Wong" <darrick.wong@...cle.com>
Signed-off-by: Yang Guo <guoyang2@...wei.com>
Signed-off-by: Shaokun Zhang <zhangshaokun@...ilicon.com>
---
 fs/xfs/xfs_mount.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index ba5b6f3b2b88..5e8314e6565e 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -1174,6 +1174,9 @@ xfs_mod_icount(
 	int64_t			delta)
 {
 	percpu_counter_add_batch(&mp->m_icount, delta, XFS_ICOUNT_BATCH);
+	if (delta > 0)
+		return 0;
+
 	if (__percpu_counter_compare(&mp->m_icount, 0, XFS_ICOUNT_BATCH) < 0) {
 		ASSERT(0);
 		percpu_counter_add(&mp->m_icount, -delta);
@@ -1188,6 +1191,9 @@ xfs_mod_ifree(
 	int64_t			delta)
 {
 	percpu_counter_add(&mp->m_ifree, delta);
+	if (delta > 0)
+		return 0;
+
 	if (percpu_counter_compare(&mp->m_ifree, 0) < 0) {
 		ASSERT(0);
 		percpu_counter_add(&mp->m_ifree, -delta);
-- 
2.7.4