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  • Maximum threads reached on mips and mipsel buildds?

    From James Cowgill@21:1/5 to Steven Capper on Tue Jul 25 18:00:03 2017
    Copy: debian-mips@lists.debian.org

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    Hi,

    [moved to debian-mips@l.d.o]

    On 24/07/17 22:48, Steven Capper wrote:
    Hi,
    I've been tweaking my tbb package for Buster, and have upgraded to
    latest upstream release and am closing off a few bugs.

    One thing I noticed is a strange failure mode for 2017~U7-2
    (targetting sid) on the mips and mipsel buildds. Logs at: https://buildd.debian.org/status/fetch.php?pkg=tbb&arch=mips&ver=2017~U7-2&stamp=1500818436&raw=0
    and, https://buildd.debian.org/status/fetch.php?pkg=tbb&arch=mipsel&ver=2017~U7-2&stamp=1500865997&raw=0

    (mips64el appears to work fine)

    The failure mode is:

    ./test_malloc_pools.exe 1:4
    Call stack info (6): ./test_malloc_pools.exe(_Z16print_call_stackv+0x8c)[0x5565ea78] ./test_malloc_pools.exe(_Z11ReportErrorPKciS0_S0_+0x40)[0x5565ec1c] ./test_malloc_pools.exe(_Z19TestFixedBufferPoolv+0x828)[0x55660b60] ./test_malloc_pools.exe(_Z8TestMainv+0x64)[0x55662af8] ./test_malloc_pools.exe(main+0x98)[0x5565e2d8] /lib/mipsel-linux-gnu/libc.so.6(__libc_start_main+0x108)[0x778ed4c8] ../../src/test/harness.h:530, assertion 0==status: NativeParallelFor: pthread_create failed

    Running it in strace gives:
    clone(child_stack=0x7f045ff0, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID, parent_tidptr=0x7f0464f8, tls=0x7f04d920, child_tidptr=0x7f0464f8) = 16753
    mmap2(NULL, 4194304, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = 0x7f047000
    mprotect(0x7f047000, 4096, PROT_NONE) = 0
    clone(child_stack=0x7f445ff0, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID, parent_tidptr=0x7f4464f8, tls=0x7f44d920, child_tidptr=0x7f4464f8) = 16754
    mmap2(NULL, 4194304, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = 0x7f447000
    mprotect(0x7f447000, 4096, PROT_NONE) = 0
    clone(child_stack=0x7f845ff0, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID, parent_tidptr=0x7f8464f8, tls=0x7f84d920, child_tidptr=0x7f8464f8) = 16755
    mmap2(NULL, 4194304, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = -1 ENOMEM (Cannot allocate memory)

    Which means it probably run out of virtual memory to allocate any more
    stacks. Since 32-bit mips is limited to 2GB of virtual memory and the
    default stack size is 4MB, this places an upper limit on the number of
    threads per process at 512. In practice it will be smaller than that
    since we have to store the heap, executables etc.

    James


    --JEPxWUdRLlohDeGJPPalBnLU76ameuIAh--

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  • From Steven Capper@21:1/5 to James Cowgill on Tue Jul 25 18:30:02 2017
    On 25 July 2017 at 15:52, James Cowgill <jcowgill@debian.org> wrote:
    Hi,

    [moved to debian-mips@l.d.o]

    On 24/07/17 22:48, Steven Capper wrote:
    Hi,
    I've been tweaking my tbb package for Buster, and have upgraded to
    latest upstream release and am closing off a few bugs.

    One thing I noticed is a strange failure mode for 2017~U7-2
    (targetting sid) on the mips and mipsel buildds. Logs at:
    https://buildd.debian.org/status/fetch.php?pkg=tbb&arch=mips&ver=2017~U7-2&stamp=1500818436&raw=0
    and,
    https://buildd.debian.org/status/fetch.php?pkg=tbb&arch=mipsel&ver=2017~U7-2&stamp=1500865997&raw=0

    (mips64el appears to work fine)

    The failure mode is:

    ./test_malloc_pools.exe 1:4
    Call stack info (6):
    ./test_malloc_pools.exe(_Z16print_call_stackv+0x8c)[0x5565ea78]
    ./test_malloc_pools.exe(_Z11ReportErrorPKciS0_S0_+0x40)[0x5565ec1c]
    ./test_malloc_pools.exe(_Z19TestFixedBufferPoolv+0x828)[0x55660b60]
    ./test_malloc_pools.exe(_Z8TestMainv+0x64)[0x55662af8]
    ./test_malloc_pools.exe(main+0x98)[0x5565e2d8]
    /lib/mipsel-linux-gnu/libc.so.6(__libc_start_main+0x108)[0x778ed4c8]
    ../../src/test/harness.h:530, assertion 0==status: NativeParallelFor:
    pthread_create failed

    Running it in strace gives:
    clone(child_stack=0x7f045ff0, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID, parent_tidptr=0x7f0464f8, tls=0x7f04d920, child_tidptr=0x7f0464f8) = 16753
    mmap2(NULL, 4194304, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = 0x7f047000
    mprotect(0x7f047000, 4096, PROT_NONE) = 0
    clone(child_stack=0x7f445ff0, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID, parent_tidptr=0x7f4464f8, tls=0x7f44d920, child_tidptr=0x7f4464f8) = 16754
    mmap2(NULL, 4194304, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = 0x7f447000
    mprotect(0x7f447000, 4096, PROT_NONE) = 0
    clone(child_stack=0x7f845ff0, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID, parent_tidptr=0x7f8464f8, tls=0x7f84d920, child_tidptr=0x7f8464f8) = 16755
    mmap2(NULL, 4194304, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = -1 ENOMEM (Cannot allocate memory)

    Which means it probably run out of virtual memory to allocate any more stacks. Since 32-bit mips is limited to 2GB of virtual memory and the
    default stack size is 4MB, this places an upper limit on the number of threads per process at 512. In practice it will be smaller than that
    since we have to store the heap, executables etc.


    Thank you James,
    Rather embarrassingly I hadn't even considered the VA space size :-).
    I can (and should) bring the default stack size down to 1MB for 32-bit
    mips. I will also double check whether or not I've introduced a
    regression in the packaging, as I think earlier versions of this
    package worked on 32-bit mips.

    Cheers,
    --
    Steve

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