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From: Matthew Wilcox <willy@infradead.org>
To: Jan Ziak <0xe2.0x9a.0x9b@gmail.com>
Cc: gregkh@linuxfoundation.org, linux-api@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-kselftest@vger.kernel.org, linux-man@vger.kernel.org,
	mtk.manpages@gmail.com, shuah@kernel.org,
	viro@zeniv.linux.org.uk
Subject: Re: [PATCH 0/3] readfile(2): a new syscall to make open/read/close faster
Date: Sun, 5 Jul 2020 04:12:08 +0100	[thread overview]
Message-ID: <20200705031208.GS25523@casper.infradead.org> (raw)
In-Reply-To: <CAODFU0qwtPTaBRbA3_ufA6N7fajhi61Sp5iE75Shdk25NSOTLA@mail.gmail.com>

On Sun, Jul 05, 2020 at 04:46:04AM +0200, Jan Ziak wrote:
> On Sun, Jul 5, 2020 at 4:16 AM Matthew Wilcox <willy@infradead.org> wrote:
> >
> > 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.
> 
> I am proposing the following:
> 
> struct readfile_t {
>   int dirfd;
>   const char *pathname;
>   void *buf;
>   size_t count;
>   int flags;
>   ssize_t retval; // set by kernel
>   int reserved; // not used by kernel
> };
> 
> int readfiles(struct readfile_t *requests, size_t count);
> 
> Returns zero if all requests succeeded, otherwise the returned value
> is non-zero (glibc wrapper: -1) and user-space is expected to check
> which requests have succeeded and which have failed. retval in
> readfile_t is set to what the single-file readfile syscall would
> return if it was called with the contents of the corresponding
> readfile_t struct.

You should probably take a look at io_uring.  That has the level of
complexity of this proposal and supports open/read/close along with many
other opcodes.

  reply	other threads:[~2020-07-05  3:12 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-05  2:06 Jan Ziak
2020-07-05  2:16 ` Matthew Wilcox
2020-07-05  2:46   ` Jan Ziak
2020-07-05  3:12     ` Matthew Wilcox [this message]
2020-07-05  3:18       ` Jan Ziak
2020-07-05  3:27         ` Matthew Wilcox
2020-07-05  4:09           ` Jan Ziak
2020-07-05 11:58             ` Greg KH
2020-07-06  6:07               ` Jan Ziak
2020-07-06 11:11                 ` Matthew Wilcox
2020-07-06 11:18                 ` Greg KH
2020-07-05  8:07           ` Vito Caputo
2020-07-05 11:44             ` Greg KH
2020-07-05 20:34               ` Vito Caputo
2020-07-05  6:32     ` Andreas Dilger
2020-07-05  7:25       ` Jan Ziak
2020-07-05 12:00         ` Greg KH
2020-07-05 11:50 ` Greg KH
2020-07-14  6:51   ` Pavel Machek
2020-07-14  8:07     ` Miklos Szeredi
2020-07-14 11:34       ` Pavel Begunkov
2020-07-14 11:55         ` Miklos Szeredi
2020-07-15  8:31           ` Pavel Begunkov
2020-07-15  8:41             ` Miklos Szeredi
2020-07-15  8:49               ` Pavel Begunkov
2020-07-15  9:00                 ` Pavel Begunkov
2020-07-15 11:17                   ` Miklos Szeredi
  -- strict thread matches above, loose matches on Subject: below --
2020-07-04 14:02 Greg Kroah-Hartman
2020-07-04 19:30 ` Al Viro
2020-07-05 11:47   ` Greg Kroah-Hartman
2020-07-06 17:25 ` Dave Martin

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