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    openvswitch: Eliminate memset() from flow_extract. · 07148121
    Jesse Gross 提交于
    As new protocols are added, the size of the flow key tends to
    increase although few protocols care about all of the fields. In
    order to optimize this for hashing and matching, OVS uses a variable
    length portion of the key. However, when fields are extracted from
    the packet we must still zero out the entire key.
    
    This is no longer necessary now that OVS implements masking. Any
    fields (or holes in the structure) which are not part of a given
    protocol will be by definition not part of the mask and zeroed out
    during lookup. Furthermore, since masking already uses variable
    length keys this zeroing operation automatically benefits as well.
    
    In principle, the only thing that needs to be done at this point
    is remove the memset() at the beginning of flow. However, some
    fields assume that they are initialized to zero, which now must be
    done explicitly. In addition, in the event of an error we must also
    zero out corresponding fields to signal that there is no valid data
    present. These increase the total amount of code but very little of
    it is executed in non-error situations.
    
    Removing the memset() reduces the profile of ovs_flow_extract()
    from 0.64% to 0.56% when tested with large packets on a 10G link.
    Suggested-by: NPravin Shelar <pshelar@nicira.com>
    Signed-off-by: NJesse Gross <jesse@nicira.com>
    Signed-off-by: NAndy Zhou <azhou@nicira.com>
    Acked-by: NPravin B Shelar <pshelar@nicira.com>
    Signed-off-by: NDavid S. Miller <davem@davemloft.net>
    07148121
flow.c 17.3 KB