On Mon, 2017-04-24 at 18:33 -0700, Stephen Hemminger wrote:
> My change (introduced in 4.11) to use find_first_clear_bit
> incorrectly assumed that the size argument was words, not bits.
Oops...
> The effect was only a small limited number of the available send
> sections were being actually used. This can cause performance loss
> with some workloads.
>
> Since map_words is now used only during initialization, it can
> be on stack instead of in per-device data.
>
> Fixes: b58a185801da ("netvsc: simplify get next send section")
> Signed-off-by: Stephen Hemminger <sthem...@microsoft.com>
Looks good to me.
Reviewed by Greg Rose <gvrose8...@gmail.com>
> ---
> drivers/net/hyperv/hyperv_net.h | 1 -
> drivers/net/hyperv/netvsc.c | 9 ++++-----
> 2 files changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
> index f9f3dba7a588..db23cb36ae5c 100644
> --- a/drivers/net/hyperv/hyperv_net.h
> +++ b/drivers/net/hyperv/hyperv_net.h
> @@ -751,7 +751,6 @@ struct netvsc_device {
> u32 send_section_cnt;
> u32 send_section_size;
> unsigned long *send_section_map;
> - int map_words;
>
> /* Used for NetVSP initialization protocol */
> struct completion channel_init_wait;
> diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> index 8dd0b8770328..15ef713d96c0 100644
> --- a/drivers/net/hyperv/netvsc.c
> +++ b/drivers/net/hyperv/netvsc.c
> @@ -236,6 +236,7 @@ static int netvsc_init_buf(struct hv_device *device)
> struct netvsc_device *net_device;
> struct nvsp_message *init_packet;
> struct net_device *ndev;
> + size_t map_words;
> int node;
>
> net_device = get_outbound_net_device(device);
> @@ -401,11 +402,9 @@ static int netvsc_init_buf(struct hv_device *device)
> net_device->send_section_size, net_device->send_section_cnt);
>
> /* Setup state for managing the send buffer. */
> - net_device->map_words = DIV_ROUND_UP(net_device->send_section_cnt,
> - BITS_PER_LONG);
> + map_words = DIV_ROUND_UP(net_device->send_section_cnt, BITS_PER_LONG);
>
> - net_device->send_section_map = kcalloc(net_device->map_words,
> - sizeof(ulong), GFP_KERNEL);
> + net_device->send_section_map = kcalloc(map_words, sizeof(ulong),
> GFP_KERNEL);
> if (net_device->send_section_map == NULL) {
> ret = -ENOMEM;
> goto cleanup;
> @@ -683,7 +682,7 @@ static u32 netvsc_get_next_send_section(struct
> netvsc_device *net_device)
> unsigned long *map_addr = net_device->send_section_map;
> unsigned int i;
>
> - for_each_clear_bit(i, map_addr, net_device->map_words) {
> + for_each_clear_bit(i, map_addr, net_device->send_section_cnt) {
> if (sync_test_and_set_bit(i, map_addr) == 0)
> return i;
> }
