Re: [Discuss-gnuradio] Memory allocation issue

[Ron Economos]

It's actually trying to allocate 3 GBytes, which seems huge. You may not have enough free memory. I would try to determine what change you made that's causing such a large allocation.

An FFT size of 2048 is still pretty small. In the DVB-T2 OFDM transmitter, even with a 16384 FFT size, it's only using 52 MBytes of shared memory.

Ron

On 10/06/2015 12:30 AM, Hitesh Kasera wrote:

At first i tried that one only but that didn't work out. Then i tried to set shared memory 8GB. The syntax i used the same
sudo sysctl kernel.shmmax=8589934592 but still getting the same error.

Hitesh

On Tue, Oct 6, 2015 at 10:51 AM, Ron Economos <address@hidden> wrote:

The correct syntax is:

sudo sysctl kernel.shmmax=2147483648

for 2 Gbytes.

Ron

On 10/05/2015 10:01 PM, Hitesh Kasera wrote:

Hello everyone,
I am trying to implement OFDM TX in GRC but with fft length 2048. according to fft length i have updated syn words, pilot carriers, pilot symbols, occupied carriers. When i run the flow graph i get this 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 1536000 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 1536000 KB
terminate called after throwing an instance of 'std::bad_alloc'
what(): std::bad_alloc

Buffer size is around 1.5GB. i tried to set kernel.shmmax to 8GB but its not working. I am using Ubuntu 14.04. Kernel and GNU details are:
GNU Radio Companion 3.7.8rc1
GNU C++ version 4.8.4
UHD_003.009.git-217-g012381d9
kernel release - 3.13.0-58-generic
kernel version - #97-Ubuntu SMP

I am new to work with GNU Radio. I am not able to correct this error. If anyone has any idea to correct this please tell me.

Best Regards
Hitesh

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