Date: Sun, 22 Jan 2006 20:14:09 +0100 From: "Wojciech A. Koszek" <dunstan@zsno.ids.czest.pl> To: Maxim.Sobolev@portaone.com Cc: freebsd-current@freebsd.org Subject: Re: [PATCH] Support for large number of md(4) disks Message-ID: <20060122191409.GB84400@zsno.ids.czest.pl> In-Reply-To: <43CF22AD.3080702@portaone.com> References: <20060114223019.GA99634@FreeBSD.czest.pl> <43CC168D.9080708@portaone.com> <20060118082804.GC4846@FreeBSD.czest.pl> <43CF22AD.3080702@portaone.com>
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On Wed, Jan 18, 2006 at 09:25:01PM -0800, Maxim Sobolev wrote: > Wojciech A. Koszek wrote: > >On Mon, Jan 16, 2006 at 01:56:29PM -0800, Maxim Sobolev wrote: > >>Hi, > > > >Hi Maxim, > > > >>IMHO there is better approach to fetch unknown amount of data from the > >>kernel using ioctl(2) facility. The main idea is that you allocate some > >>buffer of size sufficient in 95% of cases (for md(4) I think 8-16 > >>entries are enough), attach it to some structure which has size of the > >>buffer as one of its members and send pointer to that structure as an > >>argument to ioctl(2). [..] > Yes, there is a difference. I don't like your approach when you are > trying to win the race fixed amount of times (5) and then just bailing > out, asymptotic approach is better IMHO. Especially considering that > memory is cheap nowadays and you won't have any problems with allocating > space for many thousand configuration entries, even in the case when you > are really going to use only few of them. > > Regarding you assumption that meeting the situation when total number of > devices changes quickly I don't quite agree. A simple script can make > number of md(4) devices going up/down by few hundred per second easily, > your approach will behave erratically in such case. > I got some feedback from people who use md(4) in such cases. Looking at bugs@ gives me a feel there is also a real need for mdconfig -l working properly.. ...this is why updated patch is here: http://zsno.ids.czest.pl/~dunstan/FreeBSD/mdconfig-list.3.patch It starts with 16 entries in the user-space. Thanks! -- * Wojciech Koszek && <dunstan%zsno.ids.czest.pl>
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