On Thu, Sep 11, 2014 at 12:59:25PM -0700, James Bottomley wrote: > > On Tue, 2014-09-09 at 16:01 -0700, Dmitry Torokhov wrote: > > On Tuesday, September 09, 2014 03:46:23 PM James Bottomley wrote: > > > On Wed, 2014-09-10 at 07:41 +0900, Tejun Heo wrote: > > > > > > > > The thing is that we have to have dynamic mechanism to listen for > > > > device attachments no matter what and such mechanism has been in place > > > > for a long time at this point. The synchronous wait simply doesn't > > > > serve any purpose anymore and kinda gets in the way in that it makes > > > > it a possibly extremely slow process to tell whether loading of a > > > > module succeeded or not because the wait for the initial round of > > > > probe is piggybacked. > > > > > > OK, so we just fire and forget in userland ... why bother inventing an > > > elaborate new infrastructure in the kernel to do exactly what > > > > > > modprobe <mod> & > > > > > > would do? > > > > Just so we do not forget: we also want the no-modules case to also be able > > to probe asynchronously so that a slow device does not stall kernel booting. > > Yes, but we mostly do this anyway. SCSI for instance does asynchronous > scanning of attached devices (once the cards are probed) What would it do it card was a bit slow to probe? > but has a sync > point for ordering. Quite often we do not really care about ordering of devices. I mean, does it matter if your mouse is discovered before your keyboard or after? > > The problem of speeding up boot is different from the one of init > processes killing modprobes. Right. One is systemd doing stupid things, another is kernel could be smarter. > There are elements in common, but by and > large the biggest headaches at least in large device number boots have > already been tackled by the enterprise crowd (they don't like their > S390's or 1024 core NUMA systems taking half an hour to come up). Please do not position this as a mostly solved large systems problem, For us it is touchpad detection stalling kernel for 0.5-1 sec. Which is a lot given that we boot in seconds. Thanks. -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html