The Linux Kernel May Soon Default To SCSI MQ Mode

[phoronix]

Phoronix: The Linux Kernel May Soon Default To SCSI MQ Mode

It looks like the Linux kernel's SCSI code may soon switch away from its legacy code-path to the multi-queue (MQ) code by default...

http://www.phoronix.com/scan.php?page=news_item&px=Linux-SCSI-MQ-Default-Soon

[davidbepo]

this will be a welcome change, and it will make my kernel boot command line smaller

[czz0]

What will be the default scheduler?

[Zan Lynx]

Unless someone changes it, it will be "none." But they should do like the current system and introduce a build configuration. For example, the current IO scheduler has this setting:

CONFIG_DEFAULT_IOSCHED="cfq"

So there should be an equivalent

CONFIG_MQ_DEFAULT_IOSCHED="bfq"

[coder]

So, will this affect all devices with names like /dev/sda ? In other words, I assume we're not just talking about SAS, but also SATA?

[Zan Lynx]

Yes. SATA, SCSI, USB.

[stiiixy]

So, did they fix the spinning rust issues? This would be a nice default feature for my future storage which I like to run on matured kernels.

[coder]

So, did they fix the spinning rust issues? This would be a nice default feature for my future storage which I like to run on matured kernels.

The last sentence sure sounds like it:

"It has been more than one year since we tried to change the default from legacy to multi queue in SCSI. Back then we had to retract the change because of performance issues with rotating disks. In the meantime there have been a substantial amount of performance improvements, thus we can re-enable scsi-mq without a significant performance penalty."

[stiiixy]

The last sentence sure sounds like it:

No it doesn't. It's possibly implying that, but doesn't state specifically rotating drives received that performance fix.