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Documentation: update networking/page_pool.rst

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Add the new stats API, kernel config parameter, and stats structure
information to the page_pool documentation.

Signed-off-by: Joe Damato <jdamato@fastly.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Joe Damato 2022-03-01 23:55:50 -08:00 committed by David S. Miller
parent 6b95e3388b
commit a3dd98281b
1 changed files with 56 additions and 0 deletions
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56
Documentation/networking/page_pool.rst
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@ -105,6 +105,47 @@ a page will cause no race conditions is enough.
Please note the caller must not use data area after running
page_pool_put_page_bulk(), as this function overwrites it.
* page_pool_get_stats(): Retrieve statistics about the page_pool. This API
is only available if the kernel has been configured with
``CONFIG_PAGE_POOL_STATS=y``. A pointer to a caller allocated ``struct
page_pool_stats`` structure is passed to this API which is filled in. The
caller can then report those stats to the user (perhaps via ethtool,
debugfs, etc.). See below for an example usage of this API.
Stats API and structures
------------------------
If the kernel is configured with ``CONFIG_PAGE_POOL_STATS=y``, the API
``page_pool_get_stats()`` and structures described below are available. It
takes a pointer to a ``struct page_pool`` and a pointer to a ``struct
page_pool_stats`` allocated by the caller.
The API will fill in the provided ``struct page_pool_stats`` with
statistics about the page_pool.
The stats structure has the following fields::
struct page_pool_stats {
struct page_pool_alloc_stats alloc_stats;
struct page_pool_recycle_stats recycle_stats;
};
The ``struct page_pool_alloc_stats`` has the following fields:
* ``fast``: successful fast path allocations
* ``slow``: slow path order-0 allocations
* ``slow_high_order``: slow path high order allocations
* ``empty``: ptr ring is empty, so a slow path allocation was forced.
* ``refill``: an allocation which triggered a refill of the cache
* ``waive``: pages obtained from the ptr ring that cannot be added to
the cache due to a NUMA mismatch.
The ``struct page_pool_recycle_stats`` has the following fields:
* ``cached``: recycling placed page in the page pool cache
* ``cache_full``: page pool cache was full
* ``ring``: page placed into the ptr ring
* ``ring_full``: page released from page pool because the ptr ring was full
* ``released_refcnt``: page released (and not recycled) because refcnt > 1
Coding examples
===============
@ -157,6 +198,21 @@ NAPI poller
}
}
Stats
-----
.. code-block:: c
#ifdef CONFIG_PAGE_POOL_STATS
/* retrieve stats */
struct page_pool_stats stats = { 0 };
if (page_pool_get_stats(page_pool, &stats)) {
/* perhaps the driver reports statistics with ethool */
ethtool_print_allocation_stats(&stats.alloc_stats);
ethtool_print_recycle_stats(&stats.recycle_stats);
}
#endif
Driver unload
-------------