<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Mika,<div><br></div><div>With the current implementation of M3 MUTEX 1-1 as pthread mutex you are bound to have significant overhead for any locking code even in single-threaded apps. We need to move towards a thin-lock implementation for mutex (as used in modern Java implementations) to avoid overhead for uncontended locks. It's not too hard to implement. The idea is to represent a mutex as a tagged word. The word contains either NIL, the thread holding the lock, or a pointer to a full-blown (inflated) pthread mutex. We can use GC and other opportunities to deflate locks as needs. Checking the tag requires a CAS. There are other techniques that further eliminate the CAS for the uncontended case. But, generally, you should consider LOCK to be a fairly high-overhead operation for now.<div><br><div> <span class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: auto; -khtml-text-decorations-in-effect: none; text-indent: 0px; -apple-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><div style="word-wrap: break-word; -khtml-nbsp-mode: space; -khtml-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: auto; -khtml-text-decorations-in-effect: none; text-indent: 0px; -apple-text-size-adjust: auto; 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I'm not really that interested in switching<br>back and forth. I'm just a little disturbed by the sometimes huge<br>performance loss due to the introduction of kernel threads. I knew<br>that this would happen in certain highly multithreaded applications,<br>but I'm surprised it happens in a more or less single-threaded<br>application.<br><br>I think I've just been spoiled by 10 years of using SRCM3 and PM3<br>for FreeBSD w/o kernel threads in the sense that I've learned that<br>using LOCK has essentially no cost. On a shared-memory multiprocessor,<br>I really don't expect that to remain the case... physics won't allow<br>it. So now I just have to go through my code and find all the places<br>where I lock too much and remove them.<br><br>But the memory allocator and garbage collector do it too, no?<br><br>I also think that this idea of being able to use either is great.<br>Mainly single-threaded programs should definitely not use kernel<br>threads!<br><br>As for reaching the "thread locals", there is one slightly crazy<br>idea that one could borrow from Sussman and Steele: add another<br>implicit argument to every Modula-3 routine. In that argument,<br>pass a pointer to the thread locals. For EXTERNAL calls (in or<br>out), make it NIL (somehow, maybe involving pragmas), and in that<br>case (only), use the pthreads routines to access the thread locals.<br>Ok so it sounds kind of nuts, but with this approach you could avoid<br>locking or even calling into the pthreads libs almost entirely for<br>a single-threaded program. You could even have a thread-local<br>memory allocator that would only lock when it needs to request<br>memory from the "global allocator"... in fact there are lots of<br>things you can do with this sort of thing. Dynamically scoped<br>variables in Scheme (a la MacLisp?) is what they originally proposed<br>it for but then they suggested all kinds of tricks related to<br>continuations with it.<br><br> Mika<br></div></blockquote></div><br></div></div></body></html>