From mboxrd@z Thu Jan 1 00:00:00 1970 From: "David S. Miller" Subject: Re: Bug in 2.6.10 Date: Fri, 28 Jan 2005 11:46:00 -0800 Message-ID: <20050128114600.46f3a70a.davem@davemloft.net> References: <41FA9239.4010401@rapidforum.com> <20050128114251.64e0fff4@dxpl.pdx.osdl.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: webmaster@rapidforum.com, netdev@oss.sgi.com Return-path: To: Stephen Hemminger In-Reply-To: <20050128114251.64e0fff4@dxpl.pdx.osdl.net> Sender: netdev-bounce@oss.sgi.com Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org On Fri, 28 Jan 2005 11:42:51 -0800 Stephen Hemminger wrote: > On Fri, 28 Jan 2005 20:27:53 +0100 > Christian Schmid wrote: > > > Hello. > > > > In 2.6.10 there has been a "bug" introduced. You may also call it a feature, but its a crappy > > feature for big servers. It seems the kernel is dynamically adjusting the buffer-space available for > > sockets. Even if send-buffer has been set to 1024 KB, the kernel blocks at less if there are enough > > sockets in use. If you have 10 sockets with 1024 KB each, they do not block at all, using full 1024 > > KB. If you have 4000 sockets, they only use 200 KB. So it seems its blocking at 800 MB. This is > > good, if you have a 1/3 system, because else the kernel would run out of low mem. But I have a 2/2 > > system and I need them for buffers. So what can I do? Where can I adjust the "pool"? > > You can set the upper bound by setting tcp_wmem. There are three values > all documented in Documentation/networking/ip-sysctl.txt This feature is meant also to prevent remote denial of service attacks. It limits the amount of system memory TCP can consume on your system. Before this feature went in, it's really easy to remotely make a system consume %90 of system memory just with socket buffers.