[Mono-dev] Leaky JIT while running MonoDevelop

[Casey Marshall]

Oh, but: oof. I'm actually pretty sure this isn't in the JIT, but it's 
just getting blamed on the JIT because it's allocating things via glib 
-- those allocations are cached, and probably whatever is really leaking 
is just reusing the GList memory originally allocated by the JIT.


Rodrigo Kumpera wrote:
> Hi Casey,
> 
> We did a lot of work fixing many kinds of memory leaks under the runtime 
> and JIT.
> There are a few know issues, but none that would show in valgrind like 
> this. And none
> that would leak that much.
> 
> I'll take a look at this issue in the comming days to see if I can 
> narrow it down.
> 
> In the mean time, do you mind sending the whole valgrind report?
> 
> Thanks,
> Rodrigo
> 
> On Thu, Aug 14, 2008 at 3:07 PM, Casey Marshall 
> <casey.s.marshall at gmail.com <mailto:casey.s.marshall at gmail.com>> wrote:
> 
>     I've been seeing a memory leak -- or, maybe instead, "unbounded memory
>     growth" -- while running MonoDevelop (SVN code of MD, mono-2-0 SVN of
>     Mono). I've been running it under valgrind, and after running it
>     overnight, I find traces like this in the output:
> 
>      > ==7947== 862,223,392 bytes in 1,737,838 blocks are still
>     reachable in loss record 238 of 238
>      > ==7947==    at 0x4C21F8F: memalign (vg_replace_malloc.c:460)
>      > ==7947==    by 0x4C22028: posix_memalign (vg_replace_malloc.c:569)
>      > ==7947==    by 0x507D299: (within /usr/lib/libglib-2.0.so.0.1600.4)
>      > ==7947==    by 0x507E0F0: g_slice_alloc (in
>     /usr/lib/libglib-2.0.so.0.1600.4)
>      > ==7947==    by 0x506035D: g_list_prepend (in
>     /usr/lib/libglib-2.0.so.0.1600.4)
>      > ==7947==    by 0x432953: mono_arch_get_allocatable_int_vars
>     (mini-amd64.c:910)
>      > ==7947==    by 0x5579A9: mini_method_compile (mini.c:12490)
>      > ==7947==    by 0x558CF8: mono_jit_compile_method (mini.c:12819)
>      > ==7947==    by 0x42C5A2: mono_magic_trampoline
>     (mini-trampolines.c:249)
>      > ==7947==    by 0x415B164: ???
>      > ==7947==    by 0x8FCA917: ???
>      > ==7947==    by 0x85E7E9F: ???
> 
>     (there are many other traces, but they're all two orders of magnitude
>     smaller, in terms of memory size)
> 
>     I ran the same test again, this time with --optimize=-linears (which is
>     where at least the above trace came from) and without --debug, and
>     memory still grew, but not quite as quickly. I got another valgrind
>     trace out of that run:
> 
>      > ==5807== 794,797,632 bytes in 1,601,948 blocks are still
>     reachable in loss record 238 of 238
>      > ==5807==    at 0x4C21F8F: memalign (vg_replace_malloc.c:460)
>      > ==5807==    by 0x4C22028: posix_memalign (vg_replace_malloc.c:569)
>      > ==5807==    by 0x507D299: (within /usr/lib/libglib-2.0.so.0.1600.4)
>      > ==5807==    by 0x507E0F0: g_slice_alloc (in
>     /usr/lib/libglib-2.0.so.0.1600.4)
>      > ==5807==    by 0x506035D: g_list_prepend (in
>     /usr/lib/libglib-2.0.so.0.1600.4)
>      > ==5807==    by 0x52AF25: mono_allocate_stack_slots_full (mini.c:9812)
>      > ==5807==    by 0x432320: mono_arch_allocate_vars (mini-amd64.c:1137)
>      > ==5807==    by 0x558127: mini_method_compile (mini.c:12525)
>      > ==5807==    by 0x559419: mono_jit_compile_method (mini.c:12836)
>      > ==5807==    by 0x42C5E2: mono_magic_trampoline
>     (mini-trampolines.c:249)
>      > ==5807==    by 0x415B164: ???
>      > ==5807==    by 0x8BA4AAB: ???
> 
>     I think valgrind just didn't capture this one the first time, but it was
>     a factor in the memory growth.
> 
>     I suppose that because MonoDevelop uses a fair amount of dynamic code,
>     it uses the JIT a lot, which seems to be provoking this. I personally
>     can't figure out why this memory is still reachable -- these are all
>     GLists, and it looks like they are passed to g_list_free at the end. I
>     suppose either some nodes are being lost after sorting, or something
>     more subtle is going on.
> 
>     This is glib version 2.16.4-0ubuntu2, on Ubuntu 8.04, amd64.
> 
>     Thanks.
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