Comments on: Memory on the iPhone http://vafer.org/blog/20081128082605 ramblings of a creative mind Sun, 07 Mar 2010 01:54:16 +0000 http://wordpress.org/?v=2.8.4 hourly 1 By: Simo http://vafer.org/blog/20081128082605/comment-page-1#comment-59338 Simo Thu, 25 Feb 2010 02:52:18 +0000 http://vafer.org/blog/?p=700#comment-59338 Yes, as mentioned, same happens in linux. As a funny trivia, this is documented in Bugs section of malloc: <a href="http://linux.die.net/man/3/malloc" rel="nofollow">http://linux.die.net/man/3/malloc</a> Yes, as mentioned, same happens in linux. As a funny trivia, this is documented in Bugs section of malloc: http://linux.die.net/man/3/malloc

]]> By: Paul Querna http://vafer.org/blog/20081128082605/comment-page-1#comment-58990 Paul Querna Fri, 28 Nov 2008 16:33:23 +0000 http://vafer.org/blog/?p=700#comment-58990 Its called memory 'overcommit', and its a pretty standard feature on most Unixes....: http://opsmonkey.blogspot.com/2007/01/linux-memory-overcommit.html Its called memory ‘overcommit’, and its a pretty standard feature on most Unixes….:
http://opsmonkey.blogspot.com/2007/01/linux-memory-overcommit.html

]]> By: tcurdt http://vafer.org/blog/20081128082605/comment-page-1#comment-58989 tcurdt Fri, 28 Nov 2008 12:04:50 +0000 http://vafer.org/blog/?p=700#comment-58989 @philippe: wouldn't that be cool? :) I did some further tests. And it turns out using calloc or just writing some tiny little portion to the memory is not good enough. But if you access/fill the whole allocated bit you get the expected result. So seems that Vas is right - not that this is a surprise ;) ...but I still find it surprising as this has a couple of implications of malloc/calloc. Is it the same on a desktop? Did I just not notice before? That was an interesting exercise. @philippe: wouldn’t that be cool? :)

I did some further tests. And it turns out using calloc or just writing some tiny little portion to the memory is not good enough. But if you access/fill the whole allocated bit you get the expected result. So seems that Vas is right – not that this is a surprise ;)

…but I still find it surprising as this has a couple of implications of malloc/calloc. Is it the same on a desktop? Did I just not notice before? That was an interesting exercise.

]]> By: Vas the Man http://vafer.org/blog/20081128082605/comment-page-1#comment-58988 Vas the Man Fri, 28 Nov 2008 11:32:19 +0000 http://vafer.org/blog/?p=700#comment-58988 It's possibly just optimistic page assignment - pages mapped with no backing store until you actually write to them (they possibly read as zero, or may obtain a backing store on read as well). Try actually writing one byte every 4096 and see how far you can get. It’s possibly just optimistic page assignment – pages mapped with no backing store until you actually write to them (they possibly read as zero, or may obtain a backing store on read as well). Try actually writing one byte every 4096 and see how far you can get.

]]> By: philippe http://vafer.org/blog/20081128082605/comment-page-1#comment-58987 philippe Fri, 28 Nov 2008 08:39:29 +0000 http://vafer.org/blog/?p=700#comment-58987 719MB, impressive :) Did you try to use calloc insteac of malloc ? Maybe the allocation does not fail, but the memory may not be usable... 719MB, impressive :)

Did you try to use calloc insteac of malloc ? Maybe the allocation does not fail, but the memory may not be usable…

]]> By: Memory on the iPhone http://vafer.org/blog/20081128082605/comment-page-1#comment-58986 Memory on the iPhone Fri, 28 Nov 2008 07:30:39 +0000 http://vafer.org/blog/?p=700#comment-58986 [...] http://vafer.org/blog/20081128082605 asks Hoosgot, [...] [...] http://vafer.org/blog/20081128082605 asks Hoosgot, [...]

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