From: Trond Myklebust <trond.myklebust@fys.uio.no>
Subject: Re: Re: [PATCH] zerocopy NFS for 2.5.43
Date: Tue, 29 Oct 2002 16:09:24 +0100
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To: Hirokazu Takahashi <taka@valinux.co.jp>
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>>>>> " " == Hirokazu Takahashi <taka@valinux.co.jp> writes:

     > Shall we use ZERO_PAGE to pad RPC requests for the purpose of
     > its performance?  Using non-page data is a little inefficient
     > as the implementation of skbuff doesn't allow to append
     > non-page data to a skbuff which already have pages. Only pages
     > can be appneded to it.  If we didn't, TCP/IP stack would
     > allocate a new page to store the small zero-padded data.

Hmmm... What if we just drop actually storing a pointer to the
ZERO_PAGE? Instead, define the convention that

if (xdr_buf->tail[0].iov_base == NULL)
	padding = xdr_buf->tail[0].iov_len;

and just have xprt_sendmsg() magically append 'padding' bytes from
your ZERO_PAGE.

Unless, of course, you've got another use for the head_page/tail_page?

Cheers,
  Trond


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