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Message-ID: <20091127082316.GY8742@kernel.dk> Date: Fri, 27 Nov 2009 09:23:16 +0100 From: Jens Axboe <jens.axboe@...cle.com> To: Corrado Zoccolo <czoccolo@...il.com> Cc: Linux-Kernel <linux-kernel@...r.kernel.org>, Jeff Moyer <jmoyer@...hat.com>, Vivek Goyal <vgoyal@...hat.com>, mel@....ul.ie, efault@....de Subject: Re: [RFC,PATCH] cfq-iosched: improve async queue ramp up formula On Thu, Nov 26 2009, Corrado Zoccolo wrote: > The introduction of ramp-up formula for async queue depths has > slowed down dirty page reclaim, by reducing async write performance. > This patch improves the formula by considering the remaining slice. > > The new formula will allow more dispatches at the beginning of the > slice, reducing them at the end. > This will ensure that we achieve good throughput, without the risk of > overrunning the allotted timeslice. > > The threshold is automatically increased when sync I/O is not > intermingled with async, in accordance with the previous incarnation of > the formula. The slow ramp up is pretty much essential to being able to have low latency for the sync reads, so I'm afraid this will break that. I would prefer doing it through memory reclaim detection, like the other patch you and Motohiro suggested. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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