linux-kernel - Re: [RFC PATCH] getvalues(2) prototype

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Date:   Wed, 23 Mar 2022 08:16:41 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Miklos Szeredi <mszeredi@...hat.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, linux-man@...r.kernel.org,
        linux-security-module@...r.kernel.org, Karel Zak <kzak@...hat.com>,
        Ian Kent <raven@...maw.net>,
        David Howells <dhowells@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <christian@...uner.io>,
        Amir Goldstein <amir73il@...il.com>,
        James Bottomley <James.Bottomley@...senpartnership.com>
Subject: Re: [RFC PATCH] getvalues(2) prototype

On Tue, Mar 22, 2022 at 08:27:12PM +0100, Miklos Szeredi wrote:
> Add a new userspace API that allows getting multiple short values in a
> single syscall.
> 
> This would be useful for the following reasons:
> 
> - Calling open/read/close for many small files is inefficient.  E.g. on my
>   desktop invoking lsof(1) results in ~60k open + read + close calls under
>   /proc and 90% of those are 128 bytes or less.

As I found out in testing readfile():
	https://lore.kernel.org/r/20200704140250.423345-1-gregkh@linuxfoundation.org

microbenchmarks do show a tiny improvement in doing something like this,
but that's not a real-world application.

Do you have anything real that can use this that shows a speedup?

thanks,

greg k-h