From owner-freebsd-hackers@FreeBSD.ORG Fri Oct 31 12:29:51 2003 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 4D02D16A4CE; Fri, 31 Oct 2003 12:29:51 -0800 (PST) Received: from bluebox.CS.Princeton.EDU (bluebox.CS.Princeton.EDU [128.112.136.38]) by mx1.FreeBSD.org (Postfix) with ESMTP id 4BC2943F85; Fri, 31 Oct 2003 12:29:50 -0800 (PST) (envelope-from vivek@CS.Princeton.EDU) Received: from cs.princeton.edu (oakley [128.112.139.27]) (authenticated bits=0)h9VKTmFn023496 (version=TLSv1/SSLv3 cipher=RC4-MD5 bits=128 verify=NOT); Fri, 31 Oct 2003 15:29:48 -0500 (EST) Message-ID: <3FA2C63C.5000900@cs.princeton.edu> Date: Fri, 31 Oct 2003 15:29:48 -0500 From: Vivek Pai User-Agent: Mozilla/5.0 (X11; U; SunOS sun4u; en-US; rv:1.0.1) Gecko/20020920 Netscape/7.0 X-Accept-Language: en-us, en MIME-Version: 1.0 To: David Schultz References: <1066789354.21430.39.camel@boxster.onthenet.com.au> <20031022082953.GA69506@rot13.obsecurity.org> <1066816287.25609.34.camel@boxster.onthenet.com.au> <20031022095754.GA70026@rot13.obsecurity.org> <1066820436.25609.93.camel@boxster.onthenet.com.au> <20031026052854.GA20701@VARK.homeunix.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit cc: =?us-ascii@FreeBSD.ORG cc: Q cc: freebsd-hackers@freebsd.org cc: Kris Kennaway cc: iso-8859-1?Q?Sm=F8rgrav?= cc: Dag-Erling@FreeBSD.ORG Subject: Re: Some mmap observations compared to Linux 2.6/OpenBSD X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 31 Oct 2003 20:29:51 -0000 Take a look at Figure 6, page 9 in the following: http://www.cs.princeton.edu/~yruan/DeBox/debox.pdf On a 1GHz box with 1GB of memory, we were spending 4-5 milliseconds per mmap call, and that was limiting the throughput of our server on SpecWeb99. Figure 9 on page 11 shows that just getting rid of the mmap/munmap/mincore calls in this server got us a 50% performance boost on a fairly complicated workload. The SpecWeb99 workload was modeled after several web sites, so this might actually be a performance problem in the real world. If you look at figure 11, page 12, you'll see that with various improvements, our server's median latency dropped to less than 1ms. An mmap time of several milliseconds would kill that benefit. -Vivek David Schultz wrote: > Your idea of using a size-hashed freelist as well as a > location-sorted list is appealing in its simplicity. Though it > can cause a bit of fragmentation, it gives you constant time > lookup. Bonwick's vmem allocator ([1], section 4.4.2 and > following), apparently works quite well using this principle. > > But regardless of the approach, someone has yet to demonstrate > that this is actually a performance problem in the real world. ;-) > > [1] http://www.usenix.org/event/usenix01/full_papers/bonwick/ > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org" >