[ovs-dev] [PATCH] rhel: limit stack size to 2M.

[Timothy Redaelli]

On Thu, 28 Feb 2019 13:13:57 -0300
Flavio Leitner <fbl at sysclose.org> wrote:

> The default stack size in Fedora/RHEL is 8M, which means when ovs-vswitchd
> daemon starts and uses --mlockall (default), it will dirty all memory
> regions for all threads which is proportionally to the number of CPUs.
> 
> On a big host this increases memory usage to many hundreds of megabytes
> while OVS actually requires much less.
> 
> This patch relies on systemd to limit to 2M/thread. That is much more
> than the minimum documented at function ovs_thread_create():
> 
>     /* Some small systems use a default stack size as small as 80 kB, but OVS
>      * requires approximately 384 kB according to the following analysis:
>      * https://mail.openvswitch.org/pipermail/ovs-dev/2016-January/308592.html
>      *
>      * We use 512 kB to give us some margin of error. */
> 
> Signed-off-by: Flavio Leitner <fbl at sysclose.org>
> ---
>  rhel/usr_lib_systemd_system_ovs-vswitchd.service.in | 1 +
>  1 file changed, 1 insertion(+)

Without the patch:

# fgrep stack /proc/$(cat /var/run/openvswitch/ovs-vswitchd.pid)/limits
Max stack size            8388608              unlimited            bytes     
#

With the patch:

# fgrep stack /proc/$(cat /var/run/openvswitch/ovs-vswitchd.pid)/limits
Max stack size            2097152              2097152              bytes     
#

Acked-By: Timothy Redaelli <tredaelli at redhat.com>
Tested-By: Timothy Redaelli <tredaelli at redhat.com>