Re: flush and EIO errors when writepages fails

["Steve French" <smfrench@gmail.com>]

On Sat, Jun 21, 2008 at 11:28 AM, Evgeniy Polyakov <johnpol@2ka.mipt.ru> wrote:
> You can also hack into socket code like tcp_sendmsg()/tcp_sendpage()
> (the latter is not used in CIFS though)

Your point about tcp_sendpage reminds me of something I have been wondering
about for a while.  Since SunRPC switched to kernel_sendpage I have
been wondering
whether that is better or worse than kernel_sendmsg.   It looks like
in some cases
sendpage simply falls back to calling sendmsg with 1 iovec (instead of calling
tcp_sendpage which calls do_tcp_sendpages) which would end up being
slower than calling
sendmsg with a larger iovec as we do in smb_send2 in the write path.

For the write case in which we are writing pages (that are aligned)
out of the page cache to
the socket would sendpage be any faster than sendmsg?  (I wish there
was a sendmultiple
pages call where I could pass the whole list of pages).  How should a
piece of kernel
code check to see if sendpage is supported/faster and when to use
kernel_sendpage and
when to use sendmsg with the pages in the iovec

-- 
Thanks,

Steve