[PATCH net] netvsc: fix calculation of available send sections
From: Stephen Hemminger <stephen@networkplumber.org>
Date: 2017-04-25 01:33:47
My change (introduced in 4.11) to use find_first_clear_bit
incorrectly assumed that the size argument was words, not bits.
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 <redacted>
---
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; }
--
2.11.0