Memory allocation issue

GNU Radio
1

I’m writing a block that requires a large amount of data to be processed
in one iteration of the work function. If I call set_output_multiple()
with 8100 * 130 = 1053000 items (of gr_complex), I get the following
error:

gr::vmcircbuf_sysv_shm: shmget(1): Invalid argument
gr::vmcircbuf_sysv_shm: shmget(1): Invalid argument
gr::vmcircbuf_sysv_shm: shmget(1): Invalid argument
gr::buffer::allocate_buffer: failed to allocate buffer of size 16456 KB
gr::vmcircbuf_sysv_shm: shmget(1): Invalid argument
gr::vmcircbuf_sysv_shm: shmget(1): Invalid argument
gr::vmcircbuf_sysv_shm: shmget(1): Invalid argument
gr::buffer::allocate_buffer: failed to allocate buffer of size 16456 KB
terminate called after throwing an instance of ‘std::bad_alloc’
what(): std::bad_alloc

I realize that 16 Megabytes is a little large, but not astronomical.
The set_output_multiple() function does work fine with 8100 * 129
= 1044900 items (of gr_complex).

Is this some hard limitation in the shared memory library, or can it be
overridden somehow?

best regards,
Ron

2

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Hi Ron,
yep, that can be, within kernel-caused and total memory boundaries be
configured to your heart’s delight:

echo $(( 1024 * 1024 * 1024 )) > /proc/sys/kernel/shmmax

to set the maximum size shared mem buffer to 1GB.

Greetings,
Marcus

On 21.10.2014 18:12, Ron E. wrote:

gr::vmcircbuf_sysv_shm: shmget(1): Invalid argument
Is this some hard limitation in the shared memory library, or can
it be overridden somehow?

best regards, Ron

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3

Ron,

See if you can set kernel.shmmax to something higher. You can check the
current value with

sysctl kernel.shmmax

See sysctl(8).

Jeff

4

Marcus and Jeff,

 Works great. Thanks guys. BTW, the default on my Ubuntu 13.10

system
was 33,554,432 bytes.

best regards,
Ron

5

Hi Ron,

Yes, that seems to be linux kernel default:

$>cd /usr/src/kernels/3.14.19*
$>grep -REo
‘^[[:space:]]*#define[[:space:]]+SHMMAX[[:space:]]+0x[0-9a-f]+’
include/uapi/linux/shm.h:#define SHMMAX 0x2000000
$>echo $((0x2000000))
33554432

Cheers,
Marcus

PS: help, I’m being helped captive in a bad-regex factory. They feed us
mail addresses!