From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Galbraith Date: Wed, 21 May 2003 09:26:31 +0000 Subject: [Linux-ia64] Re: web page on O(1) scheduler Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org At 11:49 PM 5/20/2003 -0700, David Mosberger wrote: >Recently, I started to look into some odd performance behaviors of the >O(1) scheduler. I decided to document what I found in a web page >at: > > http://www.hpl.hp.com/research/linux/kernel/o1.php >Comments welcome. The page mentions persistent starvation. My own explorations of this issue indicate that the primary source is always selecting the highest priority queue. Combine that with the round-robin, and you have a good chance of being grossly unfair with some workloads. I know for certain that lock holders in the active array can be starved for very long periods by tasks entering higher priority queues, thereby causing even more starvation when they finally get the cpu and can release the lock (sleepers go through the roof). Try the attached overly simplistic (KISS:) diff, and watch your starvation issues be very noticably reduced. -Mike