Re: [PATCH net-next 0/2] net/sctp: Avoid allocating high order memory with kmalloc()

Hi,

On Mon, Apr 23, 2018 at 09:41:04PM +0300, Oleg Babin wrote:

Each SCTP association can have up to 65535 input and output streams.
For each stream type an array of sctp_stream_in or sctp_stream_out
structures is allocated using kmalloc_array() function. This function
allocates physically contiguous memory regions, so this can lead
to allocation of memory regions of very high order, i.e.:

  sizeof(struct sctp_stream_out) == 24,
  ((65535 * 24) / 4096) == 383 memory pages (4096 byte per page),
  which means 9th memory order.

This can lead to a memory allocation failures on the systems
under a memory stress.

Did you do performance tests while actually using these 65k streams
and with 256 (so it gets 2 pages)?

This will introduce another deref on each access to an element, but
I'm not expecting any impact due to it.

  Marcelo