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| From | glen herrmannsfeldt <gah@ugcs.caltech.edu> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: I want to ask a question... |
| Date | 2015-08-21 06:19 +0000 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <mr6fu6$nim$1@speranza.aioe.org> (permalink) |
| References | (8 earlier) <mr514a$688$1@dont-email.me> <slrnmtc48b.vvc.tTh@hangartistique.cispeo.fr> <mr59jh$b5v$1@dont-email.me> <mr5evc$24a$1@dont-email.me> <mr65hq$1eb$1@dont-email.me> |
James Kuyper <jameskuyper@verizon.net> wrote: > On 08/20/2015 04:58 PM, David Brown wrote: > ... >> I believe it is common for malloc implementations to ask the OS for >> large chunks of memory, then dish out parts of that as needed by the >> program. This way they only bother the OS on occasion, and the overhead >> for malloc is much smaller (there are no context switches or system >> calls for most allocations). Memory can only be returned to the OS if a >> whole chunk has been freed - ... > I agree with all of the above. (snip) > That doesn't strike me as a particular odd thing for a program to do. > I've seen programs that have a memory-intensive set-up phase, after > which they spend a lot of time waiting (sometimes for days or weeks at a > time) for events to happen and reacting to them, without needing > anywhere near as much memory. If I were using such a program, I'd be > very upset that it was monopolizing it's entire initial memory > requirement for the entire life of the program. Of course, a lot of > modern software hogs a lot of memory, and possibly this is one of the > reasons why. For most systems, that is virtual memory, part of each tasks own virtual address space. There have been systems with a single virtual address space for all tasks, but that is rare now. Other than that, different systems allocate real memory to tasks in different ways, some of which may be more or less efficient in different ways. How each program uses its own virtual address space can make a difference. Fragmentation in virtual space can result in more paging, and otherwise waste resources. -- glen
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Re: I want to ask a question... Gareth Owen <gwowen@gmail.com> - 2015-08-07 20:00 +0100
Re: I want to ask a question... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-07 19:04 +0000
Re: I want to ask a question... Keith Thompson <kst-u@mib.org> - 2015-08-07 15:30 -0700
Re: I want to ask a question... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-07 22:52 +0000
Re: I want to ask a question... Keith Thompson <kst-u@mib.org> - 2015-08-07 16:46 -0700
Re: I want to ask a question... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-07 23:29 +0000
Re: I want to ask a question... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-08-08 01:37 +0100
Re: I want to ask a question... Keith Thompson <kst-u@mib.org> - 2015-08-07 18:55 -0700
Re: I want to ask a question... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-08 05:51 +0000
Re: I want to ask a question... Robert Wessel <robertwessel2@yahoo.com> - 2015-08-08 01:44 -0500
Re: I want to ask a question... Ken Brody <kenbrody@spamcop.net> - 2015-08-10 12:46 -0400
Re: I want to ask a question... supercat@casperkitty.com - 2015-08-19 16:43 -0700
Re: I want to ask a question... Keith Thompson <kst-u@mib.org> - 2015-08-19 18:09 -0700
Re: I want to ask a question... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-20 01:00 +0000
Re: I want to ask a question... Keith Thompson <kst-u@mib.org> - 2015-08-19 20:25 -0700
Re: I want to ask a question... supercat@casperkitty.com - 2015-08-20 08:15 -0700
Re: I want to ask a question... Keith Thompson <kst-u@mib.org> - 2015-08-20 11:38 -0700
Re: I want to ask a question... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-20 18:47 +0000
Re: I want to ask a question... supercat@casperkitty.com - 2015-08-20 14:01 -0700
Re: I want to ask a question... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-20 16:43 +0000
Re: I want to ask a question... James Kuyper <jameskuyper@verizon.net> - 2015-08-20 13:02 -0400
Re: I want to ask a question... Tonton Th <tTh@nowhere.invalid> - 2015-08-20 17:40 +0000
Re: I want to ask a question... James Kuyper <jameskuyper@verizon.net> - 2015-08-20 15:27 -0400
Re: I want to ask a question... David Brown <david.brown@hesbynett.no> - 2015-08-20 22:58 +0200
Re: I want to ask a question... James Kuyper <jameskuyper@verizon.net> - 2015-08-20 23:24 -0400
Re: I want to ask a question... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-21 06:19 +0000
Re: I want to ask a question... Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2015-08-21 09:20 -0600
Re: I want to ask a question... supercat@casperkitty.com - 2015-08-22 12:25 -0700
Re: I want to ask a question... Robert Wessel <robertwessel2@yahoo.com> - 2015-08-23 01:33 -0500
Re: I want to ask a question... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-20 19:28 +0000
Re: I want to ask a question... Keith Thompson <kst-u@mib.org> - 2015-08-20 12:11 -0700
Re: I want to ask a question... David Brown <david.brown@hesbynett.no> - 2015-08-20 10:02 +0200
Re: I want to ask a question... raltbos@xs4all.nl (Richard Bos) - 2015-08-22 13:42 +0000
Re: I want to ask a question... supercat@casperkitty.com - 2015-08-22 12:23 -0700
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