linux-kernel - Re: [PATCH 0/3] readfile(2): a new syscall to make open/read/close faster

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Message-ID: <20200705021631.GR25523@casper.infradead.org>
Date:   Sun, 5 Jul 2020 03:16:31 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Jan Ziak <0xe2.0x9a.0x9b@...il.com>
Cc:     gregkh@...uxfoundation.org, linux-api@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-man@...r.kernel.org,
        mtk.manpages@...il.com, shuah@...nel.org, viro@...iv.linux.org.uk
Subject: Re: [PATCH 0/3] readfile(2): a new syscall to make open/read/close
 faster

On Sun, Jul 05, 2020 at 04:06:22AM +0200, Jan Ziak wrote:
> Hello
> 
> At first, I thought that the proposed system call is capable of
> reading *multiple* small files using a single system call - which
> would help increase HDD/SSD queue utilization and increase IOPS (I/O
> operations per second) - but that isn't the case and the proposed
> system call can read just a single file.
> 
> Without the ability to read multiple small files using a single system
> call, it is impossible to increase IOPS (unless an application is
> using multiple reader threads or somehow instructs the kernel to
> prefetch multiple files into memory).

What API would you use for this?

ssize_t readfiles(int dfd, char **files, void **bufs, size_t *lens);

I pretty much hate this interface, so I hope you have something better
in mind.