<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Yes, we need to implement thin locks and biased locks. These have minimal overhead for locks held mostly by just one thread.<div><br><div>
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<br><div><div>On 28 Mar 2010, at 12:24, Mika Nystrom wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div><br>In my tests, programs that acquire a lot of locks (even uncontended ones,<br>I think) run much much faster with user threads than with kernel threads.<br>Or at least they run much (several times) faster compiled with an ancient<br>PM3 than with a recent CM3, and I'm pretty sure the threading is the<br>main difference. (Given that the effect only occurs for programs that<br>acquire a lot of locks.)<br><br> Mika<br><br>=?UTF-8?Q?Dragi=C5=A1a_Duri=C4=87?= writes:<br><blockquote type="cite">CVSup w/ user threads is not faster because user threads are faster - it<br></blockquote><blockquote type="cite">is faster because it's buggy behaviour manifests only with kernel<br></blockquote><blockquote type="cite">threads. IMO.<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">Algorithm-wise - at least on Linux NPTL is O(1) decision making time, ie<br></blockquote><blockquote type="cite">switching threads. User threads are lots of linear list walking. Figure<br></blockquote><blockquote type="cite">how efficient it is. Process management "science" has gone long way<br></blockquote><blockquote type="cite">since "founding fathers" did user threads thingy.<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">d<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">On Sun, 2010-03-28 at 09:58 +0000, Jay K wrote:<br></blockquote><blockquote type="cite"><blockquote type="cite">I understand that userthreads don't scale across multiple processors.<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">But testing out cvsup lately, things are noticably much much faster<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">with user threads. At least cvsup. I haven't watched the compiler and<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">such.<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"> - Jay<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote><blockquote type="cite">-- <br></blockquote><blockquote type="cite">Dragiša Durić <<a href="mailto:dragisha@m3w.org">dragisha@m3w.org</a>><br></blockquote></div></blockquote></div><br></div></body></html>