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Date:      Sat, 13 Jan 2024 21:50:58 -0300
From:      =?UTF-8?Q?Vin=C3=ADcius_dos_Santos_Oliveira?= <vini.ipsmaker@gmail.com>
To:        Konstantin Belousov <kostikbel@gmail.com>
Cc:        Alan Somers <asomers@freebsd.org>, freebsd-threads@freebsd.org,  Konstantin Belousov <kib@freebsd.org>
Subject:   Re: aio_read2() and aio_write2()
Message-ID:  <CAK9Rve%2BuYpxWyRPwh6gxjRkisU7WPKjXicU9%2BYiqFG-=c3trvg@mail.gmail.com>
In-Reply-To: <ZaMsUn8xFKrDkJb_@kib.kiev.ua>
References:  <CAOtMX2haq%2BErvqD2PDYKUGRgdCrk2SDjtoPL-W5jR8q8_4denA@mail.gmail.com> <CAK9RveJLK9uU0twM%2BKznUNnUnsqzwoqidPN8dzNptMQ50Z7r1Q@mail.gmail.com> <CAOtMX2ijQ=KsccMyqH-yAn6SJPR7MD_yy6CF0R2vNrQ-fhUq2Q@mail.gmail.com> <ZaMsUn8xFKrDkJb_@kib.kiev.ua>

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Em s=C3=A1b., 13 de jan. de 2024 =C3=A0s 21:35, Konstantin Belousov
<kostikbel@gmail.com> escreveu:
> In principle the function of the new flag could be done like
>         aio.aio_offset =3D lseek(fd, 0, SEEK_CUR);
>         aio_read(&aio);
> with the dis-advantage of requiring two syscalls instead of one.

There are more disadvantages besides the extra syscall.

I've built a green threading framework for Lua on top of Boost.Asio.
However I also added support for sandboxed actors (capsicum and jails
on FreeBSD). For file descriptors received through SCM_RIGHTS from
sandboxed processes, I really don't want to risk blocking the thread
(DoS) going through O_NONBLOCK (file IO is always ready, and that's
why AIO exists). So, for these file descriptors (one can never know
their "type"... whether they refer to pipes and O_NONBLOCK is enough,
or they refer to files and AIO should be used), I'll use AIO as well.
On Linux I can get away by just using io_uring for everything.

Anyway, that's *another* use case. Other applications built on top of
Boost.Asio have their own reasoning for choosing between the
streaming/random_access interfaces. And they already work on Linux and
Windows.


--=20
Vin=C3=ADcius dos Santos Oliveira
https://vinipsmaker.github.io/



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