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    nfsd: keep a checksum of the first 256 bytes of request · 01a7decf
    Jeff Layton 提交于
    Now that we're allowing more DRC entries, it becomes a lot easier to hit
    problems with XID collisions. In order to mitigate those, calculate a
    checksum of up to the first 256 bytes of each request coming in and store
    that in the cache entry, along with the total length of the request.
    
    This initially used crc32, but Chuck Lever and Jim Rees pointed out that
    crc32 is probably more heavyweight than we really need for generating
    these checksums, and recommended looking at using the same routines that
    are used to generate checksums for IP packets.
    
    On an x86_64 KVM guest measurements with ftrace showed ~800ns to use
    csum_partial vs ~1750ns for crc32.  The difference probably isn't
    terribly significant, but for now we may as well use csum_partial.
    Signed-off-by: NJeff Layton <jlayton@redhat.com>
    Stones-thrown-by: NChuck Lever <chuck.lever@oracle.com>
    Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>
    01a7decf
cache.h 2.0 KB