Date: Fri, 20 Apr 2012 12:26:53 +0400 From: "Alexander V. Chernikov" <melifaro@FreeBSD.org> To: Andre Oppermann <andre@freebsd.org> Cc: net@freebsd.org, Luigi Rizzo <rizzo@iet.unipi.it>, "K. Macy" <kmacy@freebsd.org>, current@freebsd.org Subject: Re: Some performance measurements on the FreeBSD network stack Message-ID: <4F911DCD.30001@FreeBSD.org> In-Reply-To: <4F907FB4.3080400@freebsd.org> References: <20120419133018.GA91364@onelab2.iet.unipi.it> <4F907011.9080602@freebsd.org> <20120419204622.GA94904@onelab2.iet.unipi.it> <CAHM0Q_M4wcEiWGkjWxE1OjLeziQN0vM%2B4_EYS_WComZ6=j5xhA@mail.gmail.com> <4F907FB4.3080400@freebsd.org>
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On 20.04.2012 01:12, Andre Oppermann wrote: > On 19.04.2012 22:34, K. Macy wrote: >>>> This is indeed a big problem. I'm working (rough edges remain) on >>>> changing the routing table locking to an rmlock (read-mostly) which >>> >> >> This only helps if your flows aren't hitting the same rtentry. >> Otherwise you still convoy on the lock for the rtentry itself to >> increment and decrement the rtentry's reference count. > > The rtentry lock isn't obtained anymore. While the rmlock read > lock is held on the rtable the relevant information like ifp and > such is copied out. No later referencing possible. In the end > any referencing of an rtentry would be forbidden and the rtentry > lock can be removed. The second step can be optional though. > >>> i was wondering, is there a way (and/or any advantage) to use the >>> fastforward code to look up the route for locally sourced packets ? >>> >> >> If the number of peers is bounded then you can use the flowtable. Max >> PPS is much higher bypassing routing lookup. However, it doesn't scale From my experience, turning fastfwd on gives ~20-30% performance increase (10G forwarding with firewalling, 1.4MPPS). ip_forward() uses 2 lookups (ip_rtaddr + ip_output) vs 1 ip_fastfwd(). The worst current problem IMHO is number of locks packet have to traverse, not number of lookups. >> to arbitrary flow numbers. > > In theory a rmlock-only lookup into a default-route only routing > table would be faster than creating a flow table entry for every > destination. It a matter of churn though. The flowtable isn't > lockless in itself, is it? > -- WBR, Alexander
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