Date: Mon, 29 Aug 2005 20:36:41 -0700 (PDT) From: Don Lewis <truckman@FreeBSD.org> To: jd@ugcs.caltech.edu Cc: mckusick@mckusick.com, freebsd-stable@FreeBSD.org, mkb@incubus.de, markir@paradise.net.nz Subject: Re: Sysinstall automatic filesystem size generation. Message-ID: <200508300336.j7U3afcB014128@gw.catspoiler.org> In-Reply-To: <Pine.LNX.4.53.0508291847480.20467@riyal.ugcs.caltech.edu>
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On 29 Aug, Jon Dama wrote: > It seems you need to add a layer of indirection. (owing to biodone being > called merely when the drive has cached the request). What you know is > that those operations marked completed by biodone are in fact done only > after a (costly) flush cache operation is executed. > > Therefore you want to delay this operation for as long as possible, in > fact until you actually depend on biodone being honest. I.e., at the time > another operation is inserted into the WORKLIST. > > The secret I think is to keep track of which bp's marked B_DONE by > biodone that have been certified by a flush cache. Thus permitting you to > avoid some cache flushes. Furthermore, the softdep code has to be > responsible for envoking the flush cache operation when it notices that > the B_DONE flag that it cares about does not have a matching > B_REALLY_DONE flag, which every block should have that had B_DONE set > before the flush cache operation happened. I believe you are correct.
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