From: sunil.kovv...@gmail.com
Date: Mon, 7 Mar 2016 13:05:56 +0530
> From: Sunil Goutham <sgout...@cavium.com>
>
> Instead of calling get_page() for every receive buffer carved out
> of page, set page's usage count at the end, to reduce no of atomic
> calls.
>
> Signed-off-by: Sunil Goutham <sgout...@cavium.com>
> ---
> drivers/net/ethernet/cavium/thunder/nic.h | 1 +
> drivers/net/ethernet/cavium/thunder/nicvf_queues.c | 31 ++++++++++++++-----
> 2 files changed, 24 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/net/ethernet/cavium/thunder/nic.h
> b/drivers/net/ethernet/cavium/thunder/nic.h
> index 00cc915..5628aea 100644
> --- a/drivers/net/ethernet/cavium/thunder/nic.h
> +++ b/drivers/net/ethernet/cavium/thunder/nic.h
> @@ -285,6 +285,7 @@ struct nicvf {
> u32 speed;
> struct page *rb_page;
> u32 rb_page_offset;
> + u16 rb_pageref;
> bool rb_alloc_fail;
> bool rb_work_scheduled;
> struct delayed_work rbdr_work;
> diff --git a/drivers/net/ethernet/cavium/thunder/nicvf_queues.c
> b/drivers/net/ethernet/cavium/thunder/nicvf_queues.c
> index 0dd1abf..fa05e34 100644
> --- a/drivers/net/ethernet/cavium/thunder/nicvf_queues.c
> +++ b/drivers/net/ethernet/cavium/thunder/nicvf_queues.c
> @@ -18,6 +18,15 @@
> #include "q_struct.h"
> #include "nicvf_queues.h"
>
> +static void nicvf_get_page(struct nicvf *nic)
> +{
> + if (!nic->rb_pageref || !nic->rb_page)
> + return;
> +
> + atomic_add(nic->rb_pageref, &nic->rb_page->_count);
> + nic->rb_pageref = 0;
> +}
> +
> /* Poll a register for a specific value */
> static int nicvf_poll_reg(struct nicvf *nic, int qidx,
> u64 reg, int bit_pos, int bits, int val)
> @@ -81,16 +90,15 @@ static inline int nicvf_alloc_rcv_buffer(struct nicvf
> *nic, gfp_t gfp,
> int order = (PAGE_SIZE <= 4096) ? PAGE_ALLOC_COSTLY_ORDER : 0;
>
> /* Check if request can be accomodated in previous allocated page */
> - if (nic->rb_page) {
> - if ((nic->rb_page_offset + buf_len + buf_len) >
> - (PAGE_SIZE << order)) {
> - nic->rb_page = NULL;
> - } else {
> - nic->rb_page_offset += buf_len;
> - get_page(nic->rb_page);
> - }
> + if (nic->rb_page &&
> + ((nic->rb_page_offset + buf_len) < (PAGE_SIZE << order))) {
> + nic->rb_pageref++;
> + goto ret;
> }
I do not see how this can sanely work.
By deferring the atomic increment of the page count, you create a window of
time during which the consumer can release the page and prematurely free it.
I'm not applying this, as it looks extremely buggy. Sorry.
