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From: Bill Fenner <fenner@research.att.com>
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Subject: Re: sendfile(2) SF_NOPUSH flag proposal
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>1) use TF_NOPUSH to coalesce the header and the first file part 
>   or the last file part and the trailer as Matthew Dillon suggested;

Is this really necessary?

>2) use the same TF_NOPUSH to postpone the sending partial packet while
>   a reading file page from the disk;

PRUS_MORETOCOME does this too, and is quite a bit less hacky.

>3) and use PRUS_MORETOCOME to avoid partial packet after EAGAIN
>   on non-blocking socket.

Yup.

  Bill