Phoronix: Linux 3.16: Deadline I/O Scheduler Generally Leads With A SSD
There's been numerous requests lately for more disk I/O scheduler benchmarks on Phoronix of the Linux kernel and its various scheduler options. Given that there's routinely just speculation and miscommunication by individuals over the best scheduler for HDDs/SSDs, here's some fresh benchmarks for reference using the Linux 3.16 kernel.
I don't understand how you can conclude that it's the SSD that makes deadline faster since you didn't test any HDD. Maybe it's the same story with a HDD and the difference between the schedulers lies somewhere else.
Is Deadline the default I/O scheduler in Linux?
I have a eepc notebook with extremely slow SSD. What I've noted over the years is that I don't really care how fast the disk is, but whether or now the desktop remains responsive when a backgroud process is pounding the disk. Typically, can I continue web browsing while synaptic/apt is updating packages?
In the above scenario I've noted that changing scheduling and priority for synaptic and children had a large effect. Also note that on the same machine with windows xp while starting firefox/thunderbird the machine, even the mouse pointer freezes for 10 - 30 sec. (due to long stall caused by windows fsync equivalent), while doing the same on Linux is workable.
I wonder if such a scenario if sufficiently convered by the bench marks.
CFQ is supposedly already tweaked for SSDs.
CFQ has some optimizations for SSDs and if it detects a non-rotational
media which can support higher queue depth (multiple requests at in
flight at a time), then it cuts down on idling of individual queues and
all the queues move to sync-noidle tree and only tree idle remains. This
tree idling provides isolation with buffered write queues on async tree.