Messages in this thread | | | From | Jesper Dangaard Brouer <> | Date | Fri, 14 Jul 2023 20:37:39 +0200 | Subject | Re: [PATCH RFC net-next v2 2/7] net: page_pool: place frag_* fields in one cacheline |
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On 14/07/2023 19.08, Alexander Lobakin wrote: > On x86_64, frag_* fields of struct page_pool are scattered across two > cachelines despite the summary size of 24 bytes. The last field, > ::frag_users, is pushed out to the next one, sharing it with > ::alloc_stats. > All three fields are used in pretty much the same places. There are some > holes and cold members to move around. Move frag_* one block up, placing > them right after &page_pool_params perfectly at the beginning of CL2. > This doesn't do any meaningful to the second block, as those are some > destroy-path cold structures, and doesn't do anything to ::alloc_stats, > which still starts at 200-byte offset, 8 bytes after CL3 (still fitting > into 1 cacheline). > On my setup, this yields 1-2% of Mpps when using PP frags actively. > When it comes to 32-bit architectures with 32-byte CL: &page_pool_params > plus ::pad is 44 bytes, the block taken care of is 16 bytes within one > CL, so there should be at least no regressions from the actual change. > > Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com> > --- > include/net/page_pool.h | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/include/net/page_pool.h b/include/net/page_pool.h > index 829dc1f8ba6b..212d72b5cfec 100644 > --- a/include/net/page_pool.h > +++ b/include/net/page_pool.h > @@ -130,16 +130,16 @@ static inline u64 *page_pool_ethtool_stats_get(u64 *data, void *stats) > struct page_pool { > struct page_pool_params p; > > + long frag_users; > + struct page *frag_page; > + unsigned int frag_offset; > + u32 pages_state_hold_cnt;
I think this is okay, but I want to highlight that: - pages_state_hold_cnt and pages_state_release_cnt need to be kept on separate cache-lines.
> + > struct delayed_work release_dw; > void (*disconnect)(void *); > unsigned long defer_start; > unsigned long defer_warn; > > - u32 pages_state_hold_cnt; > - unsigned int frag_offset; > - struct page *frag_page; > - long frag_users; > - > #ifdef CONFIG_PAGE_POOL_STATS > /* these stats are incremented while in softirq context */ > struct page_pool_alloc_stats alloc_stats;
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