Date: Fri, 30 Apr 2010 15:00:20 -0700 From: Maxim Sobolev <sobomax@FreeBSD.org> To: Julian Elischer <julian@elischer.org> Cc: freebsd-net@FreeBSD.org, "current@freebsd.org" <current@FreeBSD.org> Subject: Re: Making IFQ_MAXLEN tunable Message-ID: <4BDB52F4.2010100@FreeBSD.org> In-Reply-To: <4BDB4CAE.20006@elischer.org> References: <4BDB3C31.4050709@sippysoft.com> <4BDB4CAE.20006@elischer.org>
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Julian Elischer wrote: > On 4/30/10 1:23 PM, Maxim Sobolev wrote: >> Hi, >> >> Many network drivers in the FreeBSD kernel use the IFQ_MAXLEN value to >> set length of the outgoing packets queue. The default value for that >> parameter is only 50, which is pretty low especially for the cases when >> the system handles lot of small packets and can cause ENOBUFS in >> applications under the load. The following patch makes IFQ_MAXLEN a >> tunable. I am also tempted to bump the default value for IFQ_MAXLEN >> 10-fold, but would like to hear what do people think about it first. >> >> http://sobomax.sippysoft.com/IFQ_MAXLEN.diff > > so just tunable? not a sysctl :-) The sysctl would require much bigger rewrite. As long as I understand the value is now cached in many instances of the ifnet structure, and some drivers even use their own queue length instead of IFQ_MAXLEN. Therefore, even if I make this parameter a sysctl one would have to destroy interface and create it again in order for the change to have an effect. Therefore, keeping it tunable would be less confusing. > patch could be a lot smaller if you defined IFQ_MAXLEN to be V_ifqmaxlen > (do different vimages want a different value?) I am not quite sure about that. AFAIK vimage is more high-level thing, while this parameter controls queue length between kernel and hardware interface driver. vimage lies above that. -Maxim
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