For 3.8.1, I would expect that the biggest mmap you can do is limited to
about 15G, so your -Xmx15G sounds about right. For trunk that got doubled,
so I am also not surprised to hear you can manage -Xmx31G,
If you are prepared to do some minor fiddling with constants, I don't see
why you can't do two more doubling steps so as to allow a 128G mmap:
To do a doubling step, do this:
1. in aspacemgr-linux.c, find this
# if VG_WORDSIZE == 8
aspacem_maxAddr = (Addr)0x1000000000ULL - 1; // 64G
Change that to (Addr)0x200...
2. in mc_main.c, find this
# define N_PRIMARY_BITS 20
3. in mc_main.c, find this
tl_assert(MASK(1) == 0xFFFFFFF000000000ULL);
Change 0xFFFFFFF000000000ULL to 0xFFFFFFE000000000ULL
ditto the other assertions
(the change moves the 1-0 boundary in the constant one bit upwards)
I suspect you may be able to get away with just (1) (worth a try), although
you'll wind up with quite a large performance hit with Memcheck when
accessing memory above the 64G boundary. Adding in (2) and (3) should
bring the performance level back to normal.
I'd be interested to hear if this actually works.
J
On 08/13/2013 09:40 PM, Maynard Johnson wrote:
> Hi,
> A user reported a problem trying to run Java under Valgrind 3.8.1 when
> specifying a large value for the Java '-Xmx' option (128G). The user was
> attempting to use Valgrind to do some analysis of "Watson" (of Jeopardy
> fame), running on a big IBM POWER7 system with tons of memory. I reproduced
> the problem using a lower value for -Xmx on my IBM POWER7 development system,
> as well as on my laptop (an Intel Core 2 Duo). On both systems, both the
> Valgrind and Java executables are 64-bit. Below is the failing output from
> my laptop:
>
> [maynard@oc3431575272 myJavaStuff]$ valgrind --tool=none java -Xmx16G
> ThreadLoop 1
> ==13873== Nulgrind, the minimal Valgrind tool
> ==13873== Copyright (C) 2002-2012, and GNU GPL'd, by Nicholas Nethercote.
> ==13873== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info
> ==13873== Command: java -Xmx16G ThreadLoop 1
> ==13873==
> JVMJ9VM015W Initialization error for library j9gc24(2): Failed to instantiate
> heap; 16G requested
> Could not create the Java virtual machine.
> ==13873==
>
> --------------------------------------------
>
> On both systems, if I decreased the -Xmx value to 15G, the error did not
> occur. Is this a known limitation? Is there any way to work around this
> issue?
>
> I dumped the /proc/<pid>/maps file on my laptop for several runs, specifying
> different values for '-Xmx' (lower than 16G, of course). For each run, I saw
> a "[heap]" entry whose size matched whatever I specified for -Xmx. On the
> POWER7 system, the /proc/<pid>/maps file didn't have a '[heap]' entry. I've
> attached maps files from the POWER7 and my laptop in case they may be of help.
>
> I also tried the same test with current upstream Valgrind. On the POWER7
> system, I did see a little improvement -- I was able to use -Xmx values up to
> 31G --but not enough improvement for the user doing the Watson analysis. I
> wasn't able to run the java test using upstream Valgrind on my laptop because
> Valgrind dies with a SIGSEGV (I'll report that problem in a separate posting).
>
> Thanks for any help anyone can offer.
> -Maynard
>
>
>
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