Messages in this thread | | | Date | Thu, 29 Mar 2012 08:36:37 +0800 | From | Tao Ma <> | Subject | Re: [PATCH] block: Make cfq_target_latency tunable through sysfs. |
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On 03/29/2012 08:32 AM, Greg KH wrote: > On Tue, Mar 27, 2012 at 04:16:53PM +0800, Tao Ma wrote: >> From: Tao Ma <boyu.mt@taobao.com> >> >> In cfq, when we calculate a time slice for a process(or a cfqq to >> be precise), we have to consider the cfq_target_latency so that all the >> sync request have an estimated latency(300ms) and it is controlled by >> cfq_target_latency. But in some hadoop test, we have found that if >> there are many processes doing sequential read(24 for example), the >> throughput is bad because every process can only work for about 25ms >> and the cfqq is switched. That leads to a higher disk seek. We can >> achive the good throughput by setting low_latency=0, but then some >> read's latency is too much for the application. >> >> So this patch makes cfq_target_latency tunable through sysfs so that >> we can tune it and find some magic number which is not bad for both >> the throughput and the read latency. > > If you add/modify sysfs files, you HAVE to also have a matching change > to Documentation/ABI. OK, I will add it in the next round. Great thanks.
Tao > > Please do so. > > thanks, > > greg k-h > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.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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