Re: [PATCH] Asynchronous scan support for libata

[Tejun Heo <htejun@gmail.com>]

Matthew Wilcox wrote:
> Last December, I posted this: http://lwn.net/Articles/213635/
> 
> Here's an updated version.  It shaves 5 seconds off boot time on my
> configuration (qla2xxx, emulex, two ata_piix, dual fusion), but could
> save more or less on other setups.
> 
> I think I can remove the 'sync' argument and code from
> ata_scsi_scan_host() now, but wanted to send out this update today.
> 
> ---
> 
> Some of the drivers (AHCI was mentioned to me as a culprit) take a long
> time to discover all the devices attached to them.  Even for ones which
> are relatively quick, if you put a lot of them in a machine, it will
> take a long time in aggregate.  This can be fixed by adding support for
> asynchronous scsi scans, which causes the time-consuming portions of
> initialisation to take place in threads.
> 
> Signed-off-by: Matthew Wilcox <matthew@wil.cx>

I think it's generally okay although it would need to spend quite some
time in -mm and we'll need to exclude several drivers which require
host-wide silence for mode programming (the current code is buggy but
sequential probing hides it pretty well) till host-wide exclusion is
implemented.

Thanks.

-- 
tejun