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mbuf: provide bulk allocation

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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>
This commit is contained in:
Huawei Xie 2016-02-28 20:44:56 +08:00 committed by Thomas Monjalon
parent bb66588304
commit 9ec201f5d6
2 changed files with 60 additions and 0 deletions
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5
doc/guides/rel_notes/release_16_04.rst
View File

@ -35,6 +35,11 @@ This section should contain new features added in this release. Sample format:
Refer to the previous release notes for examples.
* **Enabled bulk allocation of mbufs.**
A new function ``rte_pktmbuf_alloc_bulk()`` has been added to allow the user
to allocate a bulk of mbufs.
* **Virtio 1.0.**
Enabled virtio 1.0 support for virtio pmd driver.

55
lib/librte_mbuf/rte_mbuf.h
View File

@ -1335,6 +1335,61 @@ static inline struct rte_mbuf *rte_pktmbuf_alloc(struct rte_mempool *mp)
return m;
}
/**
* 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.
*