On 10/07/2017 16:50, Bart Van Assche wrote:
On Fri, 2017-06-16 at 10:27 +0200, Christoph Hellwig wrote:Remove the SCSI_MQ_DEFAULT config option and default to the blk-mq I/O path now that we had plenty of testing, and have I/O schedulers for blk-mq. The module option to disable the blk-mq path is kept around for now. Signed-off-by: Christoph Hellwig <hch@xxxxxx> --- drivers/scsi/Kconfig | 11 ----------- drivers/scsi/scsi.c | 4 ---- 2 files changed, 15 deletions(-) diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig index 3c52867dfe28..d384f4f86c26 100644 --- a/drivers/scsi/Kconfig +++ b/drivers/scsi/Kconfig @@ -47,17 +47,6 @@ config SCSI_NETLINK default n depends on NET -config SCSI_MQ_DEFAULT - bool "SCSI: use blk-mq I/O path by default" - depends on SCSI - ---help--- - This option enables the new blk-mq based I/O path for SCSI - devices by default. With the option the scsi_mod.use_blk_mq - module/boot option defaults to Y, without it to N, but it can - still be overridden either way. - - If unsure say N. - config SCSI_PROC_FS bool "legacy /proc/scsi/ support" depends on SCSI && PROC_FS diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c index 1bf274e3b2b6..3d38c6d463b8 100644 --- a/drivers/scsi/scsi.c +++ b/drivers/scsi/scsi.c @@ -800,11 +800,7 @@ MODULE_LICENSE("GPL"); module_param(scsi_logging_level, int, S_IRUGO|S_IWUSR); MODULE_PARM_DESC(scsi_logging_level, "a bit mask of logging levels"); -#ifdef CONFIG_SCSI_MQ_DEFAULT bool scsi_use_blk_mq = true; -#else -bool scsi_use_blk_mq = false; -#endif module_param_named(use_blk_mq, scsi_use_blk_mq, bool, S_IWUSR | S_IRUGO); static int __init init_scsi(void)Since a fix for the performance regression triggered by this patch will be upstream soon (see also https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git/commit/?h=for-linus&id=32825c45ff8f4cce937ab85b030dc693ceb1aa0a):
FYI, on linux-next 20170711 (which now includes the above patch Bart mentioned) we see a large performance regression on hisi_sas (LLDD does not config shost for mq).
fio read mode iops goes from ~833K (scsi_mod.use_blk_mq=n on cmdline) to ~320K
John
Acked-by: Bart Van Assche <bart.vanassche@xxxxxxx>
