From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kroah-Hartman Subject: [ 028/135] ethernet/arc/arc_emac: Fix huge delays in large file copies Date: Fri, 11 Oct 2013 12:38:29 -0700 Message-ID: <20131011193948.290109551@linuxfoundation.org> References: <20131011193945.181603934@linuxfoundation.org> Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vineet Gupta , "David S. Miller" , Alexey Brodkin , netdev@vger.kernel.org, arc-linux-dev@synopsys.com To: linux-kernel@vger.kernel.org Return-path: In-Reply-To: <20131011193945.181603934@linuxfoundation.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 3.11-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vineet Gupta [ Upstream commit 27082ee1b92f4d41e78b85fe40f6ab39673fba00 ] copying large files to a NFS mounted host was taking absurdly large time. Turns out that TX BD reclaim had a sublte bug. Loop starts off from @txbd_dirty cursor and stops when it hits a BD still in use by controller. However when it stops it needs to keep the cursor at that very BD to resume scanning in next iteration. However it was erroneously incrementing the cursor, causing the next scan(s) to fail too, unless the BD chain was completely drained out. [ARCLinux]$ ls -l -sh /disk/log.txt 17976 -rw-r--r-- 1 root root 17.5M Sep /disk/log.txt ========== Before ===================== [ARCLinux]$ time cp /disk/log.txt /mnt/. real 31m 7.95s user 0m 0.00s sys 0m 0.10s ========== After ===================== [ARCLinux]$ time cp /disk/log.txt /mnt/. real 0m 24.33s user 0m 0.00s sys 0m 0.19s Signed-off-by: Vineet Gupta Cc: Alexey Brodkin (commit_signer:3/4=75%) Cc: "David S. Miller" (commit_signer:3/4=75%) Cc: netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: arc-linux-dev@synopsys.com Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/net/ethernet/arc/emac_main.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/net/ethernet/arc/emac_main.c +++ b/drivers/net/ethernet/arc/emac_main.c @@ -149,8 +149,6 @@ static void arc_emac_tx_clean(struct net struct sk_buff *skb = tx_buff->skb; unsigned int info = le32_to_cpu(txbd->info); - *txbd_dirty = (*txbd_dirty + 1) % TX_BD_NUM; - if ((info & FOR_EMAC) || !txbd->data) break; @@ -180,6 +178,8 @@ static void arc_emac_tx_clean(struct net txbd->data = 0; txbd->info = 0; + *txbd_dirty = (*txbd_dirty + 1) % TX_BD_NUM; + if (netif_queue_stopped(ndev)) netif_wake_queue(ndev); }