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Message-ID: <20110816130350.GF26140@barfooze.de>
Date: Tue, 16 Aug 2011 15:03:50 +0200
From: Moritz Wilhelmy <ml+musl@...f.de>
To: musl@...ts.openwall.com
Subject: Re: Anti-bloat side project
Hello,
While debugging mlmmj, my mailing list manager of choice, I noted that
it calls read(2) really, really often, in order to read a single byte
out of a fd, and then read the next byte, like this:
open("/var/spool/mlmmj/foo/control/listaddress", O_RDONLY) = 4
read(4, "f", 1) = 1
read(4, "o", 1) = 1
read(4, "o", 1) = 1
read(4, "@", 1) = 1
read(4, "l", 1) = 1
read(4, "i", 1) = 1
read(4, "s", 1) = 1
read(4, "t", 1) = 1
read(4, "s", 1) = 1
read(4, ".", 1) = 1
read(4, "e", 1) = 1
read(4, "x", 1) = 1
read(4, "a", 1) = 1
read(4, "m", 1) = 1
read(4, "p", 1) = 1
read(4, "l", 1) = 1
read(4, "e", 1) = 1
read(4, ".", 1) = 1
read(4, "c", 1) = 1
read(4, "o", 1) = 1
read(4, "m", 1) = 1
read(4, "\n", 1) = 1
close(4) = 0
It does this for every file it touches as well as network connections it
reads from.
I don't know yet, how and why exactly it does it this way, but it seems
rather insane to me, so I think it might need some patches in order to
clean it up.
It turned out that attempting to subscribe someone to a mailing list
used 794 read(x, y, 1) style syscalls. I don't think I want to know how
often it calls read() in order to post a message to all members of the
list.
Maybe this could be solved by using getline(3) instead, which is in
POSIX.1-2008 and implemented on current versions of at least glibc,
FreeBSD, NetBSD and of course musl.
I will contact the mlmmj developers and try to resolve the issue.
Solar, maybe you should still wait a bit before switching openwall over
to mlmmj ;)
Best,
Moritz
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