On 9 Sep 2003 "Jon Howell" <[EMAIL PROTECTED]> wrote: > > Actually you can guess by looking at the allocated-blocks measure, > > and use this to guess whether it's preallocated zeros or sparse, > > which might be useful for backups. But there is no way around > > reading the blocks. > Sure. Bummer; that's a lot of memory bus bandwidth (having the kernel > zero-fill the blocks, then having rsync zero-compare them) wasted.
If the program mmaps the file the kernel will fill the vm with COW references to the zero page and it will be quite cheap. > Seems like a fcntl() is in order. Repeat after me: premature optimization is the root of all evil. -- Martin -- To unsubscribe or change options: http://lists.samba.org/mailman/listinfo/rsync Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html
