> -----Original Message----- > From: J. Bruce Fields [mailto:bfields@xxxxxxxxxxxx] > Sent: Monday, June 17, 2013 10:34 AM > To: Myklebust, Trond > Cc: Jeff Layton; Sandeep Joshi; linux-nfs@xxxxxxxxxxxxxxx > Subject: Re: why does nfsd write not use splice > > On Mon, Jun 17, 2013 at 11:48:18AM +0000, Myklebust, Trond wrote: > > > > On Jun 17, 2013, at 7:01 AM, Jeff Layton <jlayton@xxxxxxxxxx> wrote: > > > Encryption certainly can be a problem, but integrity isn't > > > necessarily one. > > > > > > Basically the idea would be to receive the data off the socket into > > > a set of pages and then splice those into the correct spot in the > > > local file. In both the privacy and integrity cases, you just have > > > an extra step in between. Privacy *may* mean an extra copy too > > > (though some of the crypto routines can decrypt data in place), but > > > handling integrity shouldn't. > > > > > > The tricky parts (I think) are determining how to lay out the > > > received data into the pages you eventually want to splice into the > > > file before you receive that data in, and how to deal with it when > > > the WRITE doesn't cover an entire page. > > > > Once you've copied the data one time, most of the advantage of > > splice() is gone, since a copy will then exist in processor cache > > memory and can be duplicated quickly. > > Well, worst case you could turn it off in krb5i/krb5p cases and maybe still get > some benefit in the auth_sys case? > Not if you need to copy in order to realign the data anyway... 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
