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From: "bugdal at aerifal dot cx" <sourceware-bugzilla@sourceware.org> To: glibc-bugs@sources.redhat.com Subject: [Bug malloc/14581] glibc leaks memory and do not reuse after free (leading to unlimited RSS growth) Date: Sun, 16 Sep 2012 12:46:00 -0000 [thread overview] Message-ID: <bug-14581-131-lI82411n8f@http.sourceware.org/bugzilla/> (raw) In-Reply-To: <bug-14581-131@http.sourceware.org/bugzilla/> http://sourceware.org/bugzilla/show_bug.cgi?id=14581 --- Comment #8 from Rich Felker <bugdal at aerifal dot cx> 2012-09-16 12:46:01 UTC --- > It's very simple. There is RSS and VSZ in /proc/pid/status. > RSS tells you how much physical memory was really allocated by kernel. If you > add memset() of objects after being allocated you will find that it's really > 700MB which corresponds to VSZ as well. i.e. this memory is committed. Of course, but it can't show you gaps in the heap, only the total size of the heap. > First 500 iterations are not interesting that much, cause they do not free any > previously allocated objects. > Have you noticed that array index wraps after NL and NS iterations passed and > then most interesting begins? That's why my experiment on paper had NL=4, to see quickly what happens after the index wraps. > Actually, theoretically any allocator should not ever allocate physical RAM > more then 2*allocated_size due to fragmentation on pattern like this, right? No, the theoretical limit is many orders of magnitude worse, especially with alignment constraints. Picture wanting to allocate an object of size K, but with N objects of size 1 spaced evenly every K-1 units. In this case you have N*(K-1) units of memory "free", but unable to accommodate the size-K object, thus requiring new heap space for it. This fragmentation can grow unboundedly; N can be made arbitrarily large. Also, the size-1 objects can be spaced even farther apart and still block out allocation of a size-K object if the latter has alignment requirements. I think your test case is one situation where the alignment issue matters. -- Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug.
next prev parent reply other threads:[~2012-09-16 12:46 UTC|newest] Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-09-14 9:41 [Bug malloc/14581] New: " dev at parallels dot com 2012-09-14 19:27 ` [Bug malloc/14581] " bugdal at aerifal dot cx 2012-09-15 10:40 ` dev at parallels dot com 2012-09-15 10:44 ` dev at parallels dot com 2012-09-15 12:39 ` bugdal at aerifal dot cx 2012-09-15 14:08 ` bugdal at aerifal dot cx 2012-09-15 21:00 ` bugdal at aerifal dot cx 2012-09-16 9:44 ` dev at parallels dot com 2012-09-16 12:46 ` bugdal at aerifal dot cx [this message] 2013-05-13 9:30 ` siddhesh at redhat dot com 2013-05-20 15:12 ` ondra at iuuk dot mff.cuni.cz 2013-05-20 15:39 ` siddhesh at redhat dot com 2014-06-17 4:31 ` fweimer at redhat dot com 2020-04-28 20:05 ` [Bug malloc/14581] memalign allocations are often not reused after free mail at nh2 dot me 2021-11-25 18:05 ` carlos at redhat dot com 2022-08-02 22:20 ` mirh at protonmail dot ch 2022-08-10 4:00 ` carlos at redhat dot com 2022-12-08 14:10 ` nsz at gcc dot gnu.org 2022-12-08 14:47 ` acoplan at gcc dot gnu.org 2022-12-08 16:13 ` carlos at redhat dot com 2022-12-14 21:50 ` dj at redhat dot com 2022-12-15 10:29 ` nsz at gcc dot gnu.org 2022-12-15 10:45 ` nsz at gcc dot gnu.org 2022-12-15 21:44 ` dj at redhat dot com
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