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From: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
To: Andi Kleen <ak@suse.de>
Cc: David Miller <davem@davemloft.net>,
	Ulrich Drepper <drepper@redhat.com>,
	Andrew Morton <akpm@osdl.org>, netdev <netdev@vger.kernel.org>,
	Zach Brown <zach.brown@oracle.com>,
	Christoph Hellwig <hch@infradead.org>,
	Chase Venters <chase.venters@clientec.com>,
	Johann Borck <johann.borck@densedata.com>,
	linux-kernel@vger.kernel.org, Jeff Garzik <jeff@garzik.org>,
	Jamal Hadi Salim <hadi@cyberus.ca>, Ingo Molnar <mingo@elte.hu>,
	linux-fsdevel@vger.kernel.org
Subject: Re: [take36 10/10] kevent: Kevent based generic AIO.
Date: Mon, 12 Feb 2007 15:19:40 +0300	[thread overview]
Message-ID: <20070212121940.GA31252@2ka.mipt.ru> (raw)
In-Reply-To: <p733b5bh6bp.fsf@bingen.suse.de>

On Mon, Feb 12, 2007 at 02:08:10PM +0100, Andi Kleen (ak@suse.de) wrote:
> Evgeniy Polyakov <johnpol@2ka.mipt.ru> writes:
> > 
> > aio_sendfile_path() is essentially aio_sendfile(), except that it takes
> > source filename as parameter, has a pointer to private header
> > and its size (which allows to send header and file's content in one syscall
> > instead of three (open, send, sendfile) and returns opened file descriptor.
> 
> Are you sure this is a useful optimization? Do you have numbers vs open+aio_sendfile+close? 
> 
> Compared to the cost of sending a complete file three system calls should be quite in the noise. 
> And Linux system calls are not that expensive (few hundred cycles normally) 
> 
> Adding such compound system calls would be a worrying precedent because
> I'm sure others would want them then for their favourite system call combo
> too. If they were really useful it might make more sense to have a batch() 
> system call that works for arbitary calls, but I'm not convinced yet
> it's even needed. It would be certainly ugly.

Yes, that call ends up about 10MB/sec faster for 100 1mb file transfers
over 1gbit network (78 MB/s vs 66-72 MB/s over 1 Gb network, sendfile sending server 
is one-way AMD Athlong 64 3500+), but indeed, it can be the case that async IO sending 
was main speed factor.

I added header by request from Suparna Bhattacharya - my main position
is the same about syscall overhead, but I do not that care.

> -Andi

-- 
	Evgeniy Polyakov

  reply	other threads:[~2007-02-12 12:22 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <11712796473213@2ka.mipt.ru>
2007-02-12 11:27 ` [take36 3/10] kevent: poll/select() notifications Evgeniy Polyakov
2007-02-12 11:27   ` [take36 4/10] kevent: Socket notifications Evgeniy Polyakov
2007-02-12 11:27     ` [take36 5/10] kevent: Timer notifications Evgeniy Polyakov
2007-02-12 11:27       ` [take36 6/10] kevent: Pipe notifications Evgeniy Polyakov
2007-02-12 11:27         ` [take36 7/10] kevent: Signal notifications Evgeniy Polyakov
2007-02-12 11:27           ` [take36 8/10] kevent: Kevent posix timer notifications Evgeniy Polyakov
2007-02-12 11:27             ` [take36 9/10] kevent: Private userspace notifications Evgeniy Polyakov
2007-02-12 11:27               ` [take36 10/10] kevent: Kevent based generic AIO Evgeniy Polyakov
2007-02-12 13:08                 ` Andi Kleen
2007-02-12 12:19                   ` Evgeniy Polyakov [this message]
2007-02-12 13:12                   ` Alan
2007-02-12 13:24                     ` Evgeniy Polyakov

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