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| author |   Alexander Duyck <aduyck@mirantis.com> | 2016-03-02 16:16:01 -0500 |
|---|---|---|
| committer |   Jeff Kirsher <jeffrey.t.kirsher@intel.com> | 2016-04-05 14:59:05 -0700 |
| commit | 847a1d6796c767f8b697ead60997b847a84b897b (patch) | |
| tree | 3fdd2c06bf101b77ed307ef0fd2625eb4fef39dc /drivers | |
| parent | i40e: fix errant PCIe bandwidth message (diff) | |
| download | linux-dev-847a1d6796c767f8b697ead60997b847a84b897b.tar.xz linux-dev-847a1d6796c767f8b697ead60997b847a84b897b.zip | |
e1000: Do not overestimate descriptor counts in Tx pre-check
The current code path is capable of grossly overestimating the number of
descriptors needed to transmit a new frame. This specifically occurs if
the skb contains a number of 4K pages. The issue is that the logic for
determining the descriptors needed is ((S) >> (X)) + 1. When X is 12 it
means that we were indicating that we required 2 descriptors for each 4K
page when we only needed one.
This change corrects this by instead adding (1 << (X)) - 1 to the S value
instead of adding 1 after the fact. This way we get an accurate descriptor
needed count as we are essentially doing a DIV_ROUNDUP().
Reported-by: Ivan Suzdal <isuzdal@mirantis.com>
Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/net/ethernet/intel/e1000/e1000_main.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c index 3fc7bde699ba..d213fb45855d 100644 --- a/drivers/net/ethernet/intel/e1000/e1000_main.c +++ b/drivers/net/ethernet/intel/e1000/e1000_main.c @@ -3106,7 +3106,7 @@ static int e1000_maybe_stop_tx(struct net_device *netdev, return __e1000_maybe_stop_tx(netdev, size); } -#define TXD_USE_COUNT(S, X) (((S) >> (X)) + 1) +#define TXD_USE_COUNT(S, X) (((S) + ((1 << (X)) - 1)) >> (X)) static netdev_tx_t e1000_xmit_frame(struct sk_buff *skb, struct net_device *netdev) { |