From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: [PATCH net] netvsc: fix calculation of available send sections Date: Mon, 24 Apr 2017 18:33:38 -0700 Message-ID: <20170425013338.2653-1-sthemmin@microsoft.com> Cc: netdev@vger.kernel.org, Stephen Hemminger To: davem@davemloft.net Return-path: Received: from mail-pg0-f44.google.com ([74.125.83.44]:36427 "EHLO mail-pg0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S970006AbdDYBdr (ORCPT ); Mon, 24 Apr 2017 21:33:47 -0400 Received: by mail-pg0-f44.google.com with SMTP id g2so20591922pge.3 for ; Mon, 24 Apr 2017 18:33:47 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: 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 --- 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