Eric Dumazet <eric.duma...@gmail.com> writes:
On 3/9/21 6:10 PM, Shay Agroskin wrote:
The page cache holds pages we allocated in the past during napi
cycle,
and tracks their availability status using page ref count.
The cache can hold up to 2048 pages. Upon allocating a page, we
check
whether the next entry in the cache contains an unused page,
and if so
fetch it. If the next page is already used by another entity or
if it
belongs to a different NUMA core than the napi routine, we
allocate a
page in the regular way (page from a different NUMA core is
replaced by
the newly allocated page).
This system can help us reduce the contention between different
cores
when allocating page since every cache is unique to a queue.
For reference, many drivers already use a similar strategy.
+
+/* Fetch the cached page (mark the page as used and pass it to
the caller).
+ * If the page belongs to a different NUMA than the current
one, free the cache
+ * page and allocate another one instead.
+ */
+static struct page *ena_fetch_cache_page(struct ena_ring
*rx_ring,
+ struct ena_page
*ena_page,
+ dma_addr_t *dma,
+ int current_nid)
+{
+ /* Remove pages belonging to different node than
current_nid from cache */
+ if (unlikely(page_to_nid(ena_page->page) != current_nid))
{
+
ena_increase_stat(&rx_ring->rx_stats.lpc_wrong_numa, 1,
&rx_ring->syncp);
+ ena_replace_cache_page(rx_ring, ena_page);
+ }
+
And they use dev_page_is_reusable() instead of copy/pasting this
logic.
As a bonus, they properly deal with pfmemalloc
Thanks for reviewing it, and sorry for the time it took me to
reply, I wanted to test some of the suggestions given me here
before replying.
Providing that this patchset would still be necessary for our
driver after testing the patchset Saeed suggested, I will switch
to using dev_page_is_reusable() instead of this expression.
Shay
