From: Ross S. W. W. <RW...@me...> - 2009-03-31 18:28:54
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Vladislav Bolkhovitin wrote: > Ross S. W. Walker, on 03/30/2009 10:33 PM wrote: > > I would be interested in knowing how your code defeats CFQ's extremely > > high latency? Does your code reach into the io scheduler too? If not, > > some code hints would be great. > > Hmm, CFQ doesn't have any extra processing latency, especially > "extremely", hence there is nothing to defeat. If it had, how could it > been chosen as the default? There is definitely an issue with CFQ and kernel based write processes. I belive it has to do with some of it's basica assumptions of how the workload is generated (multiple processes) and how the disks are laid out (single spindle per logical unit != hardware raid). Check out this thread: http://lkml.org/lkml/2009/2/18/47 This will of course need some detailed investigation, but there is an imposed latency in the default configuration. Maybe your code overcomes that somehow by doing what is discussed in the above thread and sharing I/O contexts between threads? -Ross ______________________________________________________________________ This e-mail, and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail, you are hereby notified that any dissemination, distribution or copying of this e-mail, and any attachments thereto, is strictly prohibited. If you have received this e-mail in error, please immediately notify the sender and permanently delete the original and any copy or printout thereof. |