From: RPraetorius AT AspenRes DOT Com (Robert Praetorius) Subject: Re: Time and motion studies of gcc and egcs and LCC 5 Feb 1998 14:30:04 -0800 Message-ID: References: <199802041912 DOT OAA07512 AT tweedledumb DOT cygnus DOT com> Reply-To: RPraetorius AT AspenRes DOT Com Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT To: ian AT cygnus DOT com Cc: gnu-win32 AT cygnus DOT com > Discarding pages in strict FIFO order seems to me like a recipe for > thrashing. I don't know about Win95, but VMS and (its closely related descendant) NT make no attempt to maintain a working set in the conventional (Denning*) meaning of the phrase: pages are trimmed from processes when the system gets short of memory, but not on any kind of LRU basis these pages are sent to a kind of limbo list* with their contents intact if a page faults and is on the limbo list, it's given back to the process (this is called a soft fault and is MUCH cheaper than having to read the page from disk) pages that stay on the limbo list too long end up getting reused for new pages Obviously there's a tradeoff between the overhead of maintaining some kind of LRU ordering and the overhead of taking lots of soft faults. Does anybody know of any studies on this tradeoff? If the perfect is the enemy of the good and the good is the enemy of the good enough, the soft fault approach is probably good enough. However, my experience with software that strongly exploits VM (e.g., Lisp environments) is that such software performs much better in a conventional working set environment (say, Twenex) than it does in a soft fault environment (say, VMS). *see http://paris.lcs.mit.edu/~bvelez/std-colls/cacm/cacm-1751.html, for one *NT calls this the standby list - go to the Performance Monitor, select Object: Memory Counter: Page Faults/sec and hit Explain. Also, AltaVisting for "standby list" and "soft fault*" turned up: http://www.tek.com/VND/Support/Release_Notes/PERFMON.html and http://www.developer.com/reference/library/0672309777/mbaxc.htm -------p--a--s--s--i--o--n-----n--e--e--d--s-----a-----f--a--c--e------- "oncology recapitulates philately" --Mark Maxson Robert M. Praetorius "balance, not symmetry" --Mark Stanley work: RPraetorius AT AspenRes DOT Com (attribution by Stigler) fun & recreation: rmp AT PopJ1 DOT MA DOT UltraNet DOT Com - For help on using this list (especially unsubscribing), send a message to "gnu-win32-request AT cygnus DOT com" with one line of text: "help".