> -----Original Message----- > From: linux-nfs-owner@xxxxxxxxxxxxxxx [mailto:linux-nfs- > owner@xxxxxxxxxxxxxxx] On Behalf Of J. Bruce Fields > Sent: Thursday, February 07, 2013 11:01 AM > To: Chuck Lever > Cc: Jeff Layton; linux-nfs@xxxxxxxxxxxxxxx > Subject: Re: [PATCH v3 2/2] nfsd: keep a checksum of the first 256 bytes of > request > > On Thu, Feb 07, 2013 at 10:51:02AM -0500, Chuck Lever wrote: > > > > On Feb 7, 2013, at 9:51 AM, Jeff Layton <jlayton@xxxxxxxxxx> wrote: > > > > > 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 the crc32 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. > > > > I'm happy to see a checksummed DRC finally become reality for the > > Linux NFS server. > > > > Have you measured the CPU utilization impact and CPU cache footprint > > of performing a CRC computation for every incoming RPC? > > Note this is over the first 256 bytes of the request--which we're probably just > about to read for xdr decoding anyway. - Would it make sense perhaps to generate the checksum as you are reading the data? - Also, is 256 bytes sufficient? How far does that get you with your average WRITE compound? - Could the integrity checksum in RPCSEC_GSS/krbi be reused as a DRC checksum? Cheers Trond -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
