On Wed, Dec 18, 2013 at 04:22:36PM +0200, Alexander Shishkin wrote: > > Still confused, if you cannot copy it into one buffer, then why can you > > copy it into a second buffer? > > It's not copied, hardware writes directly into that second buffer.
Where's the PT documentation? I can't find it in the SDM and your ISA extensions link is a generic Intel website which is friggin useless (like all corporate websites strive to be). Your actual PT patch doesn't describe how the things works either, and while I could go read the code, I'm too lazy. The thing is; why can't you zero-copy whatever buffer the hardware writes into, into the normal buffer? Machinery like that would also be useful to zero-copy bits out of the buffer right into the page-cache. > I've done the same with BTS now (as Ingo suggested) and it also benefits > from this approach. The problem with DS is that it needs physically contiguous pages is it not? So you cannot really allocate a large buffer, and you end up needing to copy or swizzle stuff. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/