linux-kernel - Re: [PATCH 00/13] VFS: Filesystem information [ver #19]

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Date:   Wed, 01 Apr 2020 09:27:29 +0100
From:   David Howells <dhowells@...hat.com>
To:     Miklos Szeredi <miklos@...redi.hu>
Cc:     dhowells@...hat.com, Ian Kent <raven@...maw.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Linux NFS list <linux-nfs@...r.kernel.org>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Anna Schumaker <anna.schumaker@...app.com>,
        "Theodore Ts'o" <tytso@....edu>,
        Linux API <linux-api@...r.kernel.org>,
        linux-ext4@...r.kernel.org,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Miklos Szeredi <mszeredi@...hat.com>,
        Christian Brauner <christian@...uner.io>,
        Jann Horn <jannh@...gle.com>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Karel Zak <kzak@...hat.com>, Jeff Layton <jlayton@...hat.com>,
        linux-fsdevel@...r.kernel.org,
        LSM <linux-security-module@...r.kernel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/13] VFS: Filesystem information [ver #19]

Miklos Szeredi <miklos@...redi.hu> wrote:

> According to dhowell's measurements processing 100k mounts would take
> about a few seconds of system time (that's the time spent by the
> kernel to retrieve the data,

But the inefficiency of mountfs - at least as currently implemented - scales
up with the number of individual values you want to retrieve, both in terms of
memory usage and time taken.

With fsinfo(), I've tried to batch values together where it makes sense - and
there's no lingering memory overhead - no extra inodes, dentries and files
required.

David