From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Ricardo Leitner Date: Mon, 23 Apr 2018 21:33:15 +0000 Subject: Re: [PATCH net-next 0/2] net/sctp: Avoid allocating high order memory with kmalloc() Message-Id: <20180423213314.GG3711@localhost.localdomain> List-Id: References: <1524508866-317485-1-git-send-email-obabin@virtuozzo.com> In-Reply-To: <1524508866-317485-1-git-send-email-obabin@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Oleg Babin Cc: netdev@vger.kernel.org, linux-sctp@vger.kernel.org, "David S. Miller" , Vlad Yasevich , Neil Horman , Xin Long , Andrey Ryabinin 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