From: Alex Belits <[email protected]>
With the existing implementation of store_rps_map(), packets are queued
in the receive path on the backlog queues of other CPUs irrespective of
whether they are isolated or not. This could add a latency overhead to
any RT workload that is running on the same CPU.
Ensure that store_rps_map() only uses available housekeeping CPUs for
storing the rps_map.
Signed-off-by: Alex Belits <[email protected]>
Signed-off-by: Nitesh Narayan Lal <[email protected]>
---
net/core/net-sysfs.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index e353b822bb15..16e433287191 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -11,6 +11,7 @@
#include <linux/if_arp.h>
#include <linux/slab.h>
#include <linux/sched/signal.h>
+#include <linux/sched/isolation.h>
#include <linux/nsproxy.h>
#include <net/sock.h>
#include <net/net_namespace.h>
@@ -741,7 +742,7 @@ static ssize_t store_rps_map(struct netdev_rx_queue *queue,
{
struct rps_map *old_map, *map;
cpumask_var_t mask;
- int err, cpu, i;
+ int err, cpu, i, hk_flags;
static DEFINE_MUTEX(rps_map_mutex);
if (!capable(CAP_NET_ADMIN))
@@ -756,6 +757,13 @@ static ssize_t store_rps_map(struct netdev_rx_queue *queue,
return err;
}
+ hk_flags = HK_FLAG_DOMAIN | HK_FLAG_WQ;
+ cpumask_and(mask, mask, housekeeping_cpumask(hk_flags));
+ if (cpumask_weight(mask) == 0) {
+ free_cpumask_var(mask);
+ return -EINVAL;
+ }
+
map = kzalloc(max_t(unsigned int,
RPS_MAP_SIZE(cpumask_weight(mask)), L1_CACHE_BYTES),
GFP_KERNEL);
--
2.18.4
On Mon, Jun 22, 2020 at 07:45:10PM -0400, Nitesh Narayan Lal wrote:
> @@ -756,6 +757,13 @@ static ssize_t store_rps_map(struct netdev_rx_queue *queue,
> return err;
> }
>
> + hk_flags = HK_FLAG_DOMAIN | HK_FLAG_WQ;
> + cpumask_and(mask, mask, housekeeping_cpumask(hk_flags));
> + if (cpumask_weight(mask) == 0) {
We have cpumask_empty() for that, which is a much more efficient way of
testing the same.
> + free_cpumask_var(mask);
> + return -EINVAL;
> + }
> +
> map = kzalloc(max_t(unsigned int,
> RPS_MAP_SIZE(cpumask_weight(mask)), L1_CACHE_BYTES),
> GFP_KERNEL);
> --
> 2.18.4
>
On 6/23/20 5:23 AM, Peter Zijlstra wrote:
> On Mon, Jun 22, 2020 at 07:45:10PM -0400, Nitesh Narayan Lal wrote:
>> @@ -756,6 +757,13 @@ static ssize_t store_rps_map(struct netdev_rx_queue *queue,
>> return err;
>> }
>>
>> + hk_flags = HK_FLAG_DOMAIN | HK_FLAG_WQ;
>> + cpumask_and(mask, mask, housekeeping_cpumask(hk_flags));
>> + if (cpumask_weight(mask) == 0) {
> We have cpumask_empty() for that, which is a much more efficient way of
> testing the same.
Yes, right.
I will make this change.
>
>> + free_cpumask_var(mask);
>> + return -EINVAL;
>> + }
>> +
>> map = kzalloc(max_t(unsigned int,
>> RPS_MAP_SIZE(cpumask_weight(mask)), L1_CACHE_BYTES),
>> GFP_KERNEL);
>> --
>> 2.18.4
>>
--
Thanks
Nitesh