Date: Fri, 18 Apr 1997 12:44:39 +0200 (MET DST) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: dufault@hda.com (Peter Dufault) Cc: hackers@freebsd.org Subject: Re: video capture driver interface to file system? Message-ID: <199704181044.MAA08521@labinfo.iet.unipi.it> In-Reply-To: <199704181112.HAA17117@hda.hda.com> from "Peter Dufault" at Apr 18, 97 07:12:36 am
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> > and probably, in addition to preallocation, make sure that your write() > > calls are aligned to the FS/device blocksize otherwise (probably) each > > write will be preceeded by a hidden read to take care of fragmentation ? > > Or you'll get an EIO somewhere along the line when you try to do > the unaligned access. Amancio is trying to avoid the buffer copy > inherent in going through the buffer cache - I'm waiting to see > what his numbers are to see if he has to do that or it just hurts > his sense of system utilization to not do it. About the only way probably the latter :) I have IDE disks (WD Caviar) streming files at about 3MB/s (sustained over about 10 minutes) with a Pentium 133 running "tv" at the same time. Even if the raw disk speed would go up to 10MB/s I doubt the copy overhead would barely slow down the process on a PPro. Luigi
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