linux-ext4 - [PATCH 0/1] [RESEND] ext4: fix lazy initialization next schedule time computation in more granular unit

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Date:   Thu, 2 Sep 2021 16:44:11 +0000
From:   Shaoying Xu <shaoyi@...zon.com>
To:     <tytso@....edu>, <adilger.kernel@...ger.ca>
CC:     <linux-ext4@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <benh@...zon.com>, <shaoyi@...zon.com>
Subject: [PATCH 0/1] [RESEND] ext4: fix lazy initialization next schedule time computation in more granular unit

Description
===========
Ext4 FS has inappropriate implementations on the next schedule time calculation
that use jiffies to measure the time for one request to zero out inode table. This
actually makes the wait time effectively dependent on CONFIG_HZ, which is
undesirable. We have observed on server systems with 100HZ some fairly long delays
in initialization as a result. Therefore, we propose to use more granular unit to
calculate the next schedule time.

Test
====
Tested the patch in stable kernel 5.10 with FS volume 2T and 3T on EC2
instances. Before the fix, instances with 250HZ finished the lazy initialization 
in around 2.4x time less than instances with 100HZ. 
After the fix, both of them finished within approximately same time. 

Patch
=====
Shaoying Xu (1):
  ext4: fix lazy initialization next schedule time computation in more
    granular unit

 fs/ext4/super.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

-- 
2.16.6