Re: [dpdk-users] rte_zmalloc() returning non-zeroed memory on FreeBSD

On 15/08/2016 18:23, Harris, James R wrote:

quoted

-----Original Message-----
From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Thomas Monjalon
Sent: Thursday, August 11, 2016 12:05 AM
To: users@dpdk.org; dev@dpdk.org; Gonzalez Monroy, Sergio; Richardson,
Bruce
Cc: Verkamp, Daniel
Subject: Re: [dpdk-dev] [dpdk-users] rte_zmalloc() returning non-zeroed
memory on FreeBSD

Hi,

2016-08-10 23:30, Verkamp, Daniel:

quoted

It seems that with DPDK 16.07, rte_zmalloc() and related functions no
longer return zeroed memory reliably on FreeBSD.

I notice that commit b78c9175118f7d61022ddc5c62ce54a1bd73cea5 ("mem:

do

quoted

not zero out memory on zmalloc") removed the explicit memset() that

used

quoted

to ensure the buffer was zeroed; its log message says:

"Zeroing out memory on rte_zmalloc_socket is not required anymore since
all allocated memory is already zeroed."

On Linux, the memory is zeroed by the kernel.
Then the zero value is maintained in the rte_malloc pool by rte_free.

quoted

However, I don't see how this is guaranteed (at least for FreeBSD), and
it is not true in practice.  I've attached a minimized reproducer program -
running it twice in a row fails reliably for me.

Is there a missing step in FreeBSD, or is it a more general problem for
other platforms?

I guess the initial value from the kernel has been verified only on Linux.
We could re-add a memset for FreeBSD.

The problem is that the FreeBSD contigmem driver does not re-zero the huge
pages each time they are mmap'd - they are only zeroed when contigmem
initially loads.  I will push a patch for this shortly.

So that is the case where we run the app more than once, right?
I missed that, I only ran it once.

Sergio