On Wed, Feb 07, 2007 at 02:11:17PM -0700, Andreas Dilger wrote: > On Feb 07, 2007 16:06 +0530, Suparna Bhattacharya wrote: > > On Wed, Feb 07, 2007 at 12:25:50AM -0800, Mingming Cao wrote: > > > - disable preallocation if the filesystem free blocks is under some low > > > watermarks, to save space for near future real block allocation? > > > > A policy decision like this is probably worth a discussion during today's call. > > > > > - is de-preallocation something worth doing? > > As discussed in the call - I don't think we can remove preallocations. > The whole point of database preallocation is to guarantee that this space > is available in the filesystem when writing into a file at random offsets > (which would otherwise be sparse). > > Similarly, persistent preallocation shouldn't be considered differently > than an efficient way of doing zero filling of blocks. At least that is > my understanding... Is this code implementing the "uninitialized extents" > for databases (via explicit preallocation via fallocate/ioctl) so that > they don't have to zero-fill large files, or is there also automatic > preallocation of space to files (e.g. for O_APPEND files)? You are right. There is no automatic preallocation of space being done here. This code just implements the explicit (persistent) preallocation of blocks via ioctl. -- Regards, Amit Arora - 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
