Hi together, > > and then in the > > kernel, we could have a loop which checks to see if the bitmap blocks > > were already in cache, and if they were, to initialize the buddy > > bitmaps pages. That way, even if subsequent memory pressure were to > > push the buddy bitmap pages and allocation bitmaps out of the cache, > > it would mean that all of the ext4_group_info structures would be > > initialized, and just having the bb_largest_free_order information > > will very much help things. > > I like the idea of keeping the high bits of the buddy bitmap in the group > descriptor, instead of just the largest free order. It takes the same > amount of space, but provides more information. If you use the reserved field for this, users don't need to reformat their disks and "only" need to use a new kernel, right? That sounds really good to me. > > Issuing readahead requests for the bitmap blocks might be good > > compromise; since they are readahead requests, as low priority > > requests they won't interfere with anything else going on, and in > > practice, unless you are starting your video recording **immediately** > > after the reboot, it should address your concern. If there is a normal recording the PVR starts some minutes (I think 2-3) before the recording starts. If an user starts the PVR, timeshift (it's a recording) might start around 30-40 seconds after mounting the disk. But if it's problematic I can let it start later. > > (Also note that for > > most people willing to hack a DVR, adding a line to /etc/rc.local is > > usually considered easier than building a new kernel from sources and > > then after making file system format changes, requiring a reformat of > > their data disk!) > > I think storing the buddy bitmap top bits in the GDT could be a COMPAT > feature. It is just a hint that could be ignored or incorrect, since > the actual bitmap would be authoritative. Yes, adding a line to rc.local is easy. Building a new kernel is also no problem, if the patch is compatible with the current used kernel versions (3.8.7 and also good would be 3.3.8 ). The PVR uses a good software management system (something like apt) and the users can update their software including kernel every day. Reformating is a problem, but if it's not preventable, users can choose between workaround and reformat. Best regards, Frank > > Cheers, Andreas > > > So it's not that I'm against solutions that involve kernel changes or > > file system format changes. It's just that I want to make sure we > > explore the entire solution space, since there are costs in terms of > > testing costs, the need to do a backup-reformat-restore pass, etc, > > etc., to some of the solutions that have been suggested so far. > > > > Regards, > > > > - Ted > -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
