Hi Jarno,
Thanks for figuring out this bug.
I erroneously thought that since commit 623540e4617e (dpif-netdev:
Streamline miss handling.) dpif_netdev_execute() could not be called
anymore inside a dp_netdev_input() frame.
I added the exact match cache on the non pmd-thread path for two reasons:
- Avoiding a branch on the fast path
- Testing the exact match cache
I thought about it a little and I do not think there¹s a way to avoid the
branch now, so I¹m ok with the approach. I¹ve tested the DPDK throughput
with the patch and it has not changed noticeably.
One comment below:
On 9/8/14, 10:07 AM, "Jarno Rajahalme" <jrajaha...@nicira.com> wrote:
>dpif_netdev_execute may be called while doing upcall processing.
>Since the context of the input port is not tracked upto this point, we
>used the chared dp->emc_cache for packet execution. Execution needs
>to be able to pass the cache to recirculation code.
>
>Typically the pmd threads use their own emc_cache, so there is little
>value in using the shared emc_cache while processing recirculation
>during packet execution. Also, whenever the shared emc_cache was
>already used while doing the upcall, the emc_mutex is already held,
>and would be locked recursively in dpif_netdev_execute(). Rather than
>changing the mutex to a recursive type, it seems more proper to not
>use any emc_cache in dpif_netdev_execute.
>
>Forthcoming new unit tests will fail with the current lock recursion.
>
>Signed-off-by: Jarno Rajahalme <jrajaha...@nicira.com>
>---
> lib/dpif-netdev.c | 42 ++++++++++++++++++------------------------
> 1 file changed, 18 insertions(+), 24 deletions(-)
>
>diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
>index 869fb55..846c329 100644
>--- a/lib/dpif-netdev.c
>+++ b/lib/dpif-netdev.c
(...)
>
>
>@@ -2240,6 +2242,10 @@ emc_processing(struct dp_netdev *dp, struct
>emc_cache *flow_cache,
> size_t n_batches, i;
> size_t notfound_cnt = 0;
>
>+ if (OVS_UNLIKELY(!flow_cache)) {
>+ return cnt;
>+ }
>+
emc_processing() is also supposed to extract the miniflows of the packets.
Returning at this point without extracting the miniflow causes undefined
behavior.
Daniele
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