From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [take13 1/3] kevent: Core files.
Date: Thu, 24 Aug 2006 21:03:22 +0100
Message-ID: <20060824200322.GA19533@infradead.org>
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Cc: lkml <linux-kernel@vger.kernel.org>,
	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>
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To: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
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One question on the implementation of kevent_user_ctl_modify/
kevent_user_ctl_remove/kevent_user_ctl_add:  What benchmarks did you
do to add the separate 'fastpath' with the single onstack ukevent
structure if there are three or less events?  I can't believe this
actually helps in practice for various reasons:

 - you add quite a lot of icache footprint by duplicating all this code
 - kmalloc is really fast
 - two or three small copy_from/to_user calls are quite a bit slower
   than one that covers the size of all of them.