]> Gerd Stolpmann <gerd@gerd-stolpmann.de> writes: > Am Donnerstag, den 29.10.2009, 21:40 +0100 schrieb Florian Weimer: >> * Goswin von Brederlow: >> >> > - The data is passed to libaio and needs to be kept alive and unmoved >> > as long as libaio knows it. >> >> It also has to be aligned to a 512-byte boundary, so you can use >> O_DIRECT. Linux does not support truely asynchronous I/O without >> O_DIRECT AFAIK, which rarely makes it worth the trouble. > > Right. There is also the question whether aio for regular files (i.e. > files backed by page cache) is continued to be supported at all - it is > well known that Linus Torvalds doesn't like it. It can happen that at > some day aio will be restricted to block devices only. > > So I wouldn't use it for production code, but it is of course still an > interesting interface. > > Gerd Damn. That seems so stupid. Then writing asynchronous will only be possible with creating a pot full of worker thread, each one writing one chunk. So you get all those chunks in random order submitted to the kernel, the kernel has to reorder them, fit them back together, write them and then wake up the right thread for each piece completed. So much extra work while libaio has all the data already in perfect structures for the kernel. And how will you do barriers when writing with threads? Wait for all threads to complete every time you hit a barrier and thereby stalling the pipeline? MfG Goswin