On Saturday, March 23, 2013 6:11:52 PM UTC+1, Linus Torvalds wrote: > On Fri, Mar 22, 2013 at 6:24 PM, Andi Kleen <a...@firstfloor.org> wrote: > > > > > Some questions and answers: > > > > - How much does it improve performance? > > > I cannot share any performance numbers at this point unfortunately. > > Also please keep in mind that the tuning is very preliminary and > > will be revised. > > If we don't know how much it helps, we can't judge whether it's worth > even discussing this patch. It adds enough complexity that it had > better be worth it, and without knowing the performance side, all we > can see are the negatives. > > Talk to your managers about this. Tell them that without performance > numbers, any patch-series like this is totally pointless.
Hello, I don't know if the thread is still actual, but I have a Core i7 4770 as my home PC, which supports TSX. I bought it *exactly* to experiment with hardware transactions. I am willing to test and benchmark kernel patches, and since I do not work for Intel I can tell all the quantitative performance differences I find. Obviously, they will be *my* results, not official Intel ones - it's up to Andi Kleen or some other Intel guy to tell if they are ok or not with this, but since CPUs with TSX are now available in shops, non-disclosure about their performance seems a bit difficult to enforce... -- I can tell from my preliminary performance results that at least for user-space RTM seems really fast. On my PC, the overhead of an empty transaction is approximately 11 nanoseconds and a minimal transaction reading and writing 2 or 3 memory addresses runs in approximately 15-20 nanoseconds. I just hope I did not violate some non-disclosure condition attached to the CPU guarantee certificate ;-) I tested it both with GCC, using inline assembler and .byte directives, and in Lisp (don't tell anybody), by writing a compiler module that defines the XBEGIN, XTEST, XABORT and XEND primitives. -- How can I help? I would start with the patches already posted by Andi, but the ones I found in LKML archives seem to belong to at least two different sets of patches: xy/31 (September 2012) and xy/29 (March 2013) and I could not find if the first ones are a prerequisite for the second. Regards, Massimiliano -- 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/
