From: Shaoying Xu <shaoyi@amazon.com>
To: <tytso@mit.edu>, <adilger.kernel@dilger.ca>
Cc: <linux-ext4@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<benh@amazon.com>, <shaoyi@amazon.com>
Subject: Re: [PATCH 0/1] [RESEND] ext4: fix lazy initialization next schedule time computation in more granular unit
Date: Mon, 20 Sep 2021 19:56:15 +0000 [thread overview]
Message-ID: <20210920195615.GB27753@amazon.com> (raw)
In-Reply-To: <20210902164412.9994-1-shaoyi@amazon.com>
Here are more context and testing details:
This issue was originally identified in Amazon Linux 2 with kernel 5.10 and
CONFIG_HZ is 250 in x86_64 while 100 in arm64. It can be reproduced by launching
EC2 instances c5.2xlarge (x86_64) and c6g.2xlarge (arm64) then measuring time to
finish ext4lazyinit thread after mounting the ext4 FS.
w/o fix in kernel 5.10
|----------------+-------------+------------|
| ext4 FS volume | c6g.2xlarge | c5.2xlarge |
|----------------+-------------+------------|
| 2T | 1842 secs | 743 secs |
|----------------+-------------+------------|
| 3T | 2690 secs | 1110 secs |
|----------------+-------------+------------|
w/ fix in kernel 5.10
|----------------+-------------+------------|
| ext4 FS volume | c6g.2xlarge | c5.2xlarge |
|----------------+-------------+------------|
| 2T | 660 secs | 544 secs |
|----------------+-------------+------------|
| 3T | 1053 secs | 932 secs |
|----------------+-------------+------------|
On Thu, Sep 02, 2021 at 04:44:11PM +0000, Shaoying Xu wrote:
> 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
>
next prev parent reply other threads:[~2021-09-20 19:58 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-02 16:44 [PATCH 0/1] [RESEND] ext4: fix lazy initialization next schedule time computation in more granular unit Shaoying Xu
2021-09-02 16:44 ` [PATCH 1/1] " Shaoying Xu
2021-09-20 19:56 ` Shaoying Xu [this message]
2021-10-07 14:21 ` [PATCH 0/1] [RESEND] " Theodore Ts'o
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