From owner-svn-src-head@FreeBSD.ORG  Mon Nov  3 19:36:06 2014
Return-Path: <owner-svn-src-head@FreeBSD.ORG>
Delivered-To: svn-src-head@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTPS id 350C39E6;
 Mon,  3 Nov 2014 19:36:06 +0000 (UTC)
Received: from phk.freebsd.dk (phk.freebsd.dk [130.225.244.222])
 by mx1.freebsd.org (Postfix) with ESMTP id D52B0EC5;
 Mon,  3 Nov 2014 19:36:05 +0000 (UTC)
Received: from critter.freebsd.dk (unknown [192.168.60.3])
 by phk.freebsd.dk (Postfix) with ESMTP id 31CE93BD2B;
 Mon,  3 Nov 2014 19:35:59 +0000 (UTC)
Received: from critter.freebsd.dk (localhost [127.0.0.1])
 by critter.freebsd.dk (8.14.9/8.14.9) with ESMTP id sA3JZutc079455;
 Mon, 3 Nov 2014 19:35:57 GMT (envelope-from phk@phk.freebsd.dk)
To: Bruce Evans <brde@optusnet.com.au>
Subject: Re: svn commit: r274017 - head/sys/kern
In-reply-to: <20141104045159.E1605@besplex.bde.org>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
References: <201411030746.sA37kpPu037113@svn.freebsd.org>
 <54573AEE.9010602@freebsd.org> <54573B87.7000801@freebsd.org>
 <54573CD2.1000702@selasky.org> <20141103092132.GH29497@dft-labs.eu>
 <20141103100847.GK53947@kib.kiev.ua> <20141104045159.E1605@besplex.bde.org>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <79453.1415043356.1@critter.freebsd.dk>
Date: Mon, 03 Nov 2014 19:35:56 +0000
Message-ID: <79454.1415043356@critter.freebsd.dk>
X-Mailman-Approved-At: Mon, 03 Nov 2014 20:10:00 +0000
Cc: Hans Petter Selasky <hps@selasky.org>, Mateusz Guzik <mjguzik@gmail.com>,
 Mateusz Guzik <mjg@freebsd.org>, jmallett@freebsd.org, svn-src-all@freebsd.org,
 svn-src-head@freebsd.org, src-committers@freebsd.org,
 Konstantin Belousov <kostikbel@gmail.com>,
 Julian Elischer <julian@freebsd.org>
X-BeenThere: svn-src-head@freebsd.org
X-Mailman-Version: 2.1.18-1
Precedence: list
List-Id: SVN commit messages for the src tree for head/-current
 <svn-src-head.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/svn-src-head>,
 <mailto:svn-src-head-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/svn-src-head/>
List-Post: <mailto:svn-src-head@freebsd.org>
List-Help: <mailto:svn-src-head-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/svn-src-head>,
 <mailto:svn-src-head-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 03 Nov 2014 19:36:06 -0000

--------
In message <20141104045159.E1605@besplex.bde.org>, Bruce Evans writes:

>This optimization is probably minor, but reminds me of other syscalls
>that would benefit using a single largish allocation up front:
>- all vfs calls that start with namei().  They allocate PATH_MAX (1K)
>   bytes and more.  An 8K stack has plently to spare after allocating
>   1K.  However, if malloc() is used then the PATH_MAX limit shouldn't
>   exist.   Only a limit to prevent denial of service is needed.

We should actually roll a new rev of all syscalls which take a path
and have them pass strlen(path)+1 into the kernel.

That would allow both precise allocation and faster copyin, followed
by a check that the last byte is (still) a NUL.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.