[dpdk-dev,v7] mbuf: provide rte_pktmbuf_alloc_bulk API
Commit Message
v7 changes:
rte_pktmbuf_alloc_bulk isn't exported as API, so shouldn't be listed in
version map
v6 changes:
reflect the changes in release notes and library version map file
revise our duff's code style a bit to make it more readable
v5 changes:
add comment about duff's device and our variant implementation
v3 changes:
move while after case 0
add context about duff's device and why we use while loop in the commit
message
v2 changes:
unroll the loop a bit to help the performance
rte_pktmbuf_alloc_bulk allocates a bulk of packet mbufs.
There is related thread about this bulk API.
http://dpdk.org/dev/patchwork/patch/4718/
Thanks to Konstantin's loop unrolling.
Attached the wiki page about duff's device. It explains the performance
optimization through loop unwinding, and also the most dramatic use of
case label fall-through.
https://en.wikipedia.org/wiki/Duff%27s_device
In this implementation, while() loop is used because we could not assume
count is strictly positive. Using while() loop saves one line of check.
Signed-off-by: Gerald Rogers <gerald.rogers@intel.com>
Signed-off-by: Huawei Xie <huawei.xie@intel.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>
---
doc/guides/rel_notes/release_16_04.rst | 3 ++
lib/librte_mbuf/rte_mbuf.h | 55 ++++++++++++++++++++++++++++++++++
2 files changed, 58 insertions(+)
Comments
2016-02-28 20:44, Huawei Xie:
> v7 changes:
> rte_pktmbuf_alloc_bulk isn't exported as API, so shouldn't be listed in
> version map
>
> v6 changes:
> reflect the changes in release notes and library version map file
> revise our duff's code style a bit to make it more readable
>
> v5 changes:
> add comment about duff's device and our variant implementation
>
> v3 changes:
> move while after case 0
> add context about duff's device and why we use while loop in the commit
> message
>
> v2 changes:
> unroll the loop a bit to help the performance
>
> rte_pktmbuf_alloc_bulk allocates a bulk of packet mbufs.
>
> There is related thread about this bulk API.
> http://dpdk.org/dev/patchwork/patch/4718/
> Thanks to Konstantin's loop unrolling.
>
> Attached the wiki page about duff's device. It explains the performance
> optimization through loop unwinding, and also the most dramatic use of
> case label fall-through.
> https://en.wikipedia.org/wiki/Duff%27s_device
>
> In this implementation, while() loop is used because we could not assume
> count is strictly positive. Using while() loop saves one line of check.
>
> Signed-off-by: Gerald Rogers <gerald.rogers@intel.com>
> Signed-off-by: Huawei Xie <huawei.xie@intel.com>
> Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
> Acked-by: Olivier Matz <olivier.matz@6wind.com>
Applied, thanks
@@ -46,6 +46,9 @@ This section should contain new features added in this release. Sample format:
* **Added vhost-user live migration support.**
+* **Enable bulk allocation of mbufs.**
+ A new function ``rte_pktmbuf_alloc_bulk()`` has been added to allow the user
+ to allocate a bulk of mbufs.
Resolved Issues
---------------
@@ -1336,6 +1336,61 @@ static inline struct rte_mbuf *rte_pktmbuf_alloc(struct rte_mempool *mp)
}
/**
+ * Allocate a bulk of mbufs, initialize refcnt and reset the fields to default
+ * values.
+ *
+ * @param pool
+ * The mempool from which mbufs are allocated.
+ * @param mbufs
+ * Array of pointers to mbufs
+ * @param count
+ * Array size
+ * @return
+ * - 0: Success
+ */
+static inline int rte_pktmbuf_alloc_bulk(struct rte_mempool *pool,
+ struct rte_mbuf **mbufs, unsigned count)
+{
+ unsigned idx = 0;
+ int rc;
+
+ rc = rte_mempool_get_bulk(pool, (void **)mbufs, count);
+ if (unlikely(rc))
+ return rc;
+
+ /* To understand duff's device on loop unwinding optimization, see
+ * https://en.wikipedia.org/wiki/Duff's_device.
+ * Here while() loop is used rather than do() while{} to avoid extra
+ * check if count is zero.
+ */
+ switch (count % 4) {
+ case 0:
+ while (idx != count) {
+ RTE_MBUF_ASSERT(rte_mbuf_refcnt_read(mbufs[idx]) == 0);
+ rte_mbuf_refcnt_set(mbufs[idx], 1);
+ rte_pktmbuf_reset(mbufs[idx]);
+ idx++;
+ case 3:
+ RTE_MBUF_ASSERT(rte_mbuf_refcnt_read(mbufs[idx]) == 0);
+ rte_mbuf_refcnt_set(mbufs[idx], 1);
+ rte_pktmbuf_reset(mbufs[idx]);
+ idx++;
+ case 2:
+ RTE_MBUF_ASSERT(rte_mbuf_refcnt_read(mbufs[idx]) == 0);
+ rte_mbuf_refcnt_set(mbufs[idx], 1);
+ rte_pktmbuf_reset(mbufs[idx]);
+ idx++;
+ case 1:
+ RTE_MBUF_ASSERT(rte_mbuf_refcnt_read(mbufs[idx]) == 0);
+ rte_mbuf_refcnt_set(mbufs[idx], 1);
+ rte_pktmbuf_reset(mbufs[idx]);
+ idx++;
+ }
+ }
+ return 0;
+}
+
+/**
* Attach packet mbuf to another packet mbuf.
*
* After attachment we refer the mbuf we attached as 'indirect',