linux-kernel - Re: Upcoming: Notifications, FS notifications and fsinfo()

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Message-ID: <2590640.1585757211@warthog.procyon.org.uk>
Date:   Wed, 01 Apr 2020 17:06:51 +0100
From:   David Howells <dhowells@...hat.com>
To:     Miklos Szeredi <miklos@...redi.hu>
Cc:     dhowells@...hat.com, Lennart Poettering <mzxreary@...inter.de>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>, dray@...hat.com,
        Karel Zak <kzak@...hat.com>,
        Miklos Szeredi <mszeredi@...hat.com>,
        Steven Whitehouse <swhiteho@...hat.com>,
        Jeff Layton <jlayton@...hat.com>, Ian Kent <raven@...maw.net>,
        andres@...razel.de, keyrings@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Aleksa Sarai <cyphar@...har.com>
Subject: Re: Upcoming: Notifications, FS notifications and fsinfo()

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

> I've still not heard a convincing argument in favor of a syscall.

>From your own results, scanning 10000 mounts through mountfs and reading just
two values from each is an order of magnitude slower without the effect of the
dentry/inode caches.  It gets faster on the second run because the mountfs
dentries and inodes are cached - but at a cost of >205MiB of RAM.  And it's
*still* slower than fsinfo().

David