Date: Fri, 18 Nov 2011 23:10:11 +0100 From: Juergen Lock <nox@jelal.kn-bremen.de> To: Tim Kientzle <tim@kientzle.com> Cc: Alexander Best <arundel@freebsd.org>, Juergen Lock <nox@jelal.kn-bremen.de>, freebsd-hackers@freebsd.org Subject: Re: easy way to determine if a stream or fd is seekable Message-ID: <20111118221011.GA99985@triton8.kn-bremen.de> In-Reply-To: <B06B2304-A1BC-49A3-A811-F05625138D58@kientzle.com> References: <20111115202450.GA73512@freebsd.org> <20111116102239.GA2687@britannica.bec.de> <20111116131428.GA40723@freebsd.org> <20111116232152.GC21793@britannica.bec.de> <20111117002438.GA55931@freebsd.org> <201111172055.pAHKtZso061118@triton8.kn-bremen.de> <B06B2304-A1BC-49A3-A811-F05625138D58@kientzle.com>
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On Fri, Nov 18, 2011 at 12:00:07PM -0800, Tim Kientzle wrote: > > On Nov 17, 2011, at 12:55 PM, Juergen Lock wrote: > > >> > >> After a few experiments, bsdtar stopped using lseek() on > >> FreeBSD for anything other than regular files and block > >> devices. I believe there are other things that do support > >> seeking, but I don't believe there is an accurate mechanism > >> for determining whether lseek() is correctly supported. > > > > Ah is that the reason why my patch never made it into FreeBSD 9? > > I'm talking about this thread, where I also commented on seeking > > on tape: > > > > http://docs.freebsd.org/cgi/mid.cgi?20100220101724.GA26604 > > (Re: "tar tfv /dev/cd0" speedup patch) > > > > entire thread here: > > http://markmail.org/message/nfznipqik3tuhbqp > > > > Cheers, > > Juergen (who would still like to see a faster "tar tfv /dev/cd0"... :) > > I would like to see that as well. > > Take a look at > > http://libarchive.googlecode.com/svn/trunk/libarchive/archive_read_open_filename.c > > Especially the comments about detecting "disk-like" devices. > I rewrote a bunch of this code to introduce an explicit > notion of "strategy" so that we could optimize access > to a variety of different devices. > > This code has a notion of "disk-like" file descriptors and > some optimizations for such. There are some comments > in there outlining similar optimizations that could be made > for "tape-like" or "socket-like" devices. Ah so it's `just' a slow release cycle? % grep DIOCGMEDIASIZE /home/ncvs/src/lib/libarchive/archive_read_open_filename.c,v % When will we see this code in FreeBSD? 10.0? 9.1? 8.3? :) Curious... Juergen
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