From: Jens Axboe <firstname.lastname@example.org> To: Tejun Heo <email@example.com> Cc: Robert Hancock <firstname.lastname@example.org>, linux-kernel <email@example.com>, firstname.lastname@example.org, email@example.com, Nicolas.Mailhot@LaPoste.net, Jeff Garzik <firstname.lastname@example.org>, Alan Cox <email@example.com>, Mark Lord <firstname.lastname@example.org>, Ric Wheeler <email@example.com>, Dongjun Shin <firstname.lastname@example.org>, Hannes Reinecke <email@example.com> Subject: Re: libata FUA revisited Date: Wed, 21 Feb 2007 09:46:13 +0100 [thread overview] Message-ID: <20070221084613.GB3924@kernel.dk> (raw) In-Reply-To: <45DC04DF.firstname.lastname@example.org> On Wed, Feb 21 2007, Tejun Heo wrote: > [cc'ing Ric, Hannes and Dongjun, Hello. Feel free to drag other people in.] > > Robert Hancock wrote: > > Jens Axboe wrote: > >> But we can't really change that, since you need the cache flushed before > >> issuing the FUA write. I've been advocating for an ordered bit for > >> years, so that we could just do: > >> > >> 3. w/FUA+ORDERED > >> > >> normal operation -> barrier issued -> write barrier FUA+ORDERED > >> -> normal operation resumes > >> > >> So we don't have to serialize everything both at the block and device > >> level. I would have made FUA imply this already, but apparently it's not > >> what MS wanted FUA for, so... The current implementations take the FUA > >> bit (or WRITE FUA) as a hint to boost it to head of queue, so you are > >> almost certainly going to jump ahead of already queued writes. Which we > >> of course really do not. > > Yeah, I think if we have tagged write command and flush tagged (or > barrier tagged) things can be pretty efficient. Again, I'm much more > comfortable with separate opcodes for those rather than bits changing > the behavior. ORDERED+FUA NCQ would still be preferable to an NCQ enabled flush command, though. > Another idea Dongjun talked about while drinking in LSF was ranged > flush. Not as flexible/efficient as the previous option but much less > intrusive and should help quite a bit, I think. But that requires extensive tracking, I'm not so sure the implementation of that for barriers would be very clean. It'd probably be good for fsync, though. -- Jens Axboe
next prev parent reply other threads:[~2007-02-21 8:46 UTC|newest] Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <fa.S80SRyQbD/hm4SxliPUKU88BaCo@ifi.uio.no> 2007-02-12 5:47 ` Robert Hancock [not found] ` <fa.Q/csgyCHkAsD84yi+bN78H1WNNM@ifi.uio.no> 2007-02-13 0:23 ` Robert Hancock 2007-02-13 15:20 ` Tejun Heo 2007-02-14 0:07 ` Robert Hancock 2007-02-14 0:50 ` Tejun Heo 2007-02-15 18:00 ` Jens Axboe 2007-02-19 19:46 ` Robert Hancock 2007-02-21 8:37 ` Tejun Heo 2007-02-21 8:46 ` Jens Axboe [this message] 2007-02-21 8:57 ` Tejun Heo 2007-02-21 9:01 ` Jens Axboe 2007-02-22 22:44 ` Ric Wheeler 2007-02-22 22:40 ` Ric Wheeler 2007-02-21 14:06 ` Robert Hancock 2007-02-22 22:34 ` Ric Wheeler 2007-02-23 0:04 ` Robert Hancock 2007-02-21 8:44 ` Jens Axboe 2007-02-12 3:25 Robert Hancock 2007-02-12 8:31 ` Tejun Heo 2007-02-16 18:14 ` Jeff Garzik
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