Messages in this thread | | | Date | Sat, 05 Mar 2016 21:47:00 +0100 | From | "Thomas Schmitt" <> | Subject | Re: SCSI sr driver: parallel writes to optical serialized which hurts performance (sr_mutex) |
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Hi,
as developer of libburn i got several user complaints about poor concurrent throughput. Since last year i suffer from it myself on kernel 3.16 of Debian 8. Before i had 2.6.18 which did very well in that aspect.
An old workaround for IDE master-slave concurrency problems brings a certain degree of relief on some drives. See http://libburnia-project.org/wiki/ConcurrentLinuxSr
But the much better solution would be to remove the need for the global lock shared by all ioctl(SG_IO) to all /dev/sr*.
Given the old reports of Otto Meta about possible race conditions with drives at the same IDE controller, and the rareness of IDE attached drives nowadays, i propose to keep the global sr_mutex lock for IDE attached drives. Question is how this can be determined from the device parameters of the calls in question: struct block_device *bdev struct gendisk *disk struct scsi_cd *cd
Have a nice day :)
Thomas
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