linux-ext4 - Re: fsck memory usage

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Message-ID: <CAEUQceh8oX9TsOR-rtn44QtegGSGH_+QHm9GPcoVPqHGJMhWHw@mail.gmail.com>
Date:	Wed, 1 May 2013 08:12:14 +0530
From:	Subranshu Patel <spatel.ml@...il.com>
To:	"Theodore Ts'o" <tytso@....edu>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: fsck memory usage

> What version of e2fsprogs are you using? There has been a number of

> changes made to improve both CPU and memory utilization in more recent

> versions of e2fsprogs.


I am using version 1.41.12


>> Then I performed metadata corruption - 10% of the files, 10% of the

>> directories and some superblock attributes using debugfs. Then I

>> executed fsck to find a memory usage of around 8GB, a much larger

>> value.


> It's going to depend on what sort of metadata corruption was suffered.

> If you need to do pass 1b/c/d fix ups, it will need more memory.

> That's pretty much unavoidable, but it's also not the common case. In

> most use cases, if those cases require using swap, that's generally OK

> if it's the rare case, and not the common case. That's why it's not

> something I've really been worried about.

I used the sar command for tracking memory usage. The total memory
usage reported by sar command is around 8GB, but it includes the
buffer and cache memory.

memused = 8GB

buffer = 6.7GB

cache = negligible (some MBs)

So I think the effective memory usage will be 1.3GB (8 - 6.7). So the
memory reported under buffer and cache is available for use (if any
other process requires it). Please correct my understanding.

--
Subranshu
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