Date: Fri, 26 Oct 2001 20:47:27 +0900 From: Keiichi SHIMA / =?ISO-2022-JP?B?GyRCRWc3RDBsGyhC?= <keiichi@iij.ad.jp> To: Bosko Milekic <bmilekic@technokratis.com>, David Malone <dwmalone@maths.tcd.ie>, Luigi Rizzo <rizzo@aciri.org>, Alfred Perlstein <bright@mu.org>, net@FreeBSD.ORG Subject: Re: performance issues with M_PREPEND on clusters Message-ID: <86u1wmlj1s.wl@keiichi01.osaka.iij.ad.jp> In-Reply-To: <20011026110635.B14635@walton.maths.tcd.ie> References: <20011023110307.A34494@iguana.aciri.org> <20011023132813.I15052@elvis.mu.org> <20011023114650.C34494@iguana.aciri.org> <20011023140034.M15052@elvis.mu.org> <20011023140628.A36095@iguana.aciri.org> <20011023185759.A328@technokratis.com> <20011026110635.B14635@walton.maths.tcd.ie>
next in thread | previous in thread | raw e-mail | index | archive | help
Hi, I am one of the KAME members.
> The only problem I can see with this tack is that we might end up
> with M_LEADINGSPACE macro which does something different to the
> same macro in {Net,Open}BSD. I guess we should check what their
> macros do at the moment.
Right. And we will have a problem if someone changes the semantics of
M_LEADINGSPACE. The M_LEADINGSPACE macro of Net/OpenBSD does the same
as the current FreeBSD does, that is, returns 0 if M_EXT is set.
> When I looked at this question last year I think I found that there
> were few enough places in the kernel which used M_LEADINGSPACE, so
> it should be fairly easy to check them. However, I think several
> of the uses were in KAME code.
The patch posted first by Luigi is safe because the patch doesn't
change any semantics of M_LEADINGSPACE. I think it (and the patch)
reasonbale that M_LEADINGSPACE returns 0 when the mbuf (cluster) is
not writable and the real space when the mbuf (cluster) is writable.
But, I disagree the later proposal from Bosko that changes the meaning
of M_LEADINGSPACE. This leads more ifdefs in the shared code
(ex. KAME, maybe other cross-platform projects) and the code
complexity.
---
Keiichi SHIMA
IIJ Research Laboratory <keiichi@iij.ad.jp>
KAME Project <keiichi@kame.net>
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-net" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?86u1wmlj1s.wl>