Jim Buzbee wrote: > > Alan Cox wrote: > > > > > Andrew.Stevens@xxxxxxxxxxxxxxx wrote: > > > > - Put bluntly: ext2 is not good for video capture > > > > > > Mount the partition with the synchronous option. > > > > uggh. For 2.2 use O_SYNC so you just slow down the video writer thread and > > stream the I/O, for 2.4 make use of O_DIRECT to raw device if possible for > > even better behaviour Not sure I understand how this would help. Certainly synchronous makes little difference. The problem is the capture thread being starved due to large peaks in disk acitivty caused by internal FS house-keeping around file closure / file inactivity on big files. What are O_DIRECT's semantics? > What about the option of mmap'ing windows into the output file? Would > the setup overhead be worth it? The hope would be that data could go > from the video input driver to the output file system while minimizing > the number of copies. I will be investigating various options over the next week or so. The issue definately isn't an excessively high median data-rate (we're talking 4MB/sec max. sometimes as little as 500KB/sec). Copying overhead shouldn't be a problem. The machine load is miniscule during this activity... Is suspect a simple work-around would be to pre-create the files and then over-write them thus elminating file-system activity associated with block allocation. Either that or better coding in the capture thread to prevent it getting held too long in blocking I/O... I'll find out soon enough ;-) Andrew
