Re: FUA and TCQ

2016-09-27 Thread Michael van Elst
i...@bsdimp.com (Warner Losh) writes: >I've not used any m.2 devices. These tests were raw dd's of 128k I/Os >with one thread of execution, so no effective queueing at all. gossam: {4} dd if=/dev/rdk0 bs=128k of=/dev/null count=10 10+0 records in 10+0 records out 1310720 bytes

Re: FUA and TCQ

2016-09-26 Thread Warner Losh
On Mon, Sep 26, 2016 at 8:27 AM, Michael van Elst wrote: > i...@bsdimp.com (Warner Losh) writes: > >>NVMe is even worse. There's one drive that w/o queueing I can barely >>get 1GB/s out of. With queueing and multiple requests I can get the >>spec sheet rated 3.6GB/s. Here

Re: FUA and TCQ

2016-09-26 Thread Michael van Elst
b...@softjar.se (Johnny Billquist) writes: >Good point. In which case (if I read you right), it's not the reordering >that matters, but the simple case of being able to queue up several >operations, to keep the disk busy. For sequential reading we are currently limited to 8 operations in

Re: FUA and TCQ

2016-09-26 Thread Michael van Elst
i...@bsdimp.com (Warner Losh) writes: >NVMe is even worse. There's one drive that w/o queueing I can barely >get 1GB/s out of. With queueing and multiple requests I can get the >spec sheet rated 3.6GB/s. Here queueing is critical for Netflix to get to >90-93Gbps that our 100Gbps boxes can do

Re: FUA and TCQ (was: Plan: journalling fixes for WAPBL)

2016-09-24 Thread Thor Lancelot Simon
On Fri, Sep 23, 2016 at 01:02:26PM +, paul.kon...@dell.com wrote: > > > On Sep 23, 2016, at 5:49 AM, Edgar Fu?? wrote: > > > >> The whole point of tagged queueing is to let you *not* set [the write > >> cache] bit in the mode pages and still get good performance. > >

Re: FUA and TCQ (was: Plan: journalling fixes for WAPBL)

2016-09-23 Thread Paul.Koning
> On Sep 23, 2016, at 5:49 AM, Edgar Fuß wrote: > >> The whole point of tagged queueing is to let you *not* set [the write >> cache] bit in the mode pages and still get good performance. > I don't get that. My understanding was that TCQ allowed the drive to re-order >

Re: FUA and TCQ

2016-09-23 Thread Warner Losh
On Fri, Sep 23, 2016 at 8:05 AM, Thor Lancelot Simon wrote: > Our storage stack's inability to use tags with SATA targets is a huge > gating factor for performance with real workloads (the residual use of > the kernel lock at and below the bufq layer is another). FreeBSD's

Re: FUA and TCQ

2016-09-23 Thread Thor Lancelot Simon
On Fri, Sep 23, 2016 at 09:38:08AM -0400, Greg Troxel wrote: > > Johnny Billquist writes: > > > With rotating rust, the order of operations can make a huge difference > > in speed. With SSDs you don't have those seek times to begin with, so > > I would expect the gains to be

Re: FUA and TCQ

2016-09-23 Thread Johnny Billquist
On 2016-09-23 15:38, Greg Troxel wrote: Johnny Billquist writes: With rotating rust, the order of operations can make a huge difference in speed. With SSDs you don't have those seek times to begin with, so I would expect the gains to be marginal. For reordering, I agree

Re: FUA and TCQ

2016-09-23 Thread Greg Troxel
Johnny Billquist writes: > With rotating rust, the order of operations can make a huge difference > in speed. With SSDs you don't have those seek times to begin with, so > I would expect the gains to be marginal. For reordering, I agree with you, but the SSD speeds are so high

Re: FUA and TCQ

2016-09-23 Thread Johnny Billquist
On 2016-09-23 13:05, David Holland wrote: On Fri, Sep 23, 2016 at 11:49:50AM +0200, Edgar Fu? wrote: > > The whole point of tagged queueing is to let you *not* set [the write > > cache] bit in the mode pages and still get good performance. > > I don't get that. My understanding was that TCQ

Re: FUA and TCQ

2016-09-23 Thread Manuel Bouyer
On Fri, Sep 23, 2016 at 01:13:09PM +0200, Edgar Fuß wrote: > > You can have more than one in flight at a time. > My SCSI knowledge is probably out-dated. How can I have several commands > in flight concurrently? This is what tagged queueing is for. -- Manuel Bouyer

Re: FUA and TCQ

2016-09-23 Thread Edgar Fuß
> You can have more than one in flight at a time. My SCSI knowledge is probably out-dated. How can I have several commands in flight concurrently?

Re: FUA and TCQ

2016-09-23 Thread Johnny Billquist
On 2016-09-23 11:49, Edgar Fuß wrote: The whole point of tagged queueing is to let you *not* set [the write cache] bit in the mode pages and still get good performance. I don't get that. My understanding was that TCQ allowed the drive to re-order commands within the bounds described by the

Re: FUA and TCQ (was: Plan: journalling fixes for WAPBL)

2016-09-23 Thread David Holland
On Fri, Sep 23, 2016 at 11:49:50AM +0200, Edgar Fu? wrote: > > The whole point of tagged queueing is to let you *not* set [the write > > cache] bit in the mode pages and still get good performance. > > I don't get that. My understanding was that TCQ allowed the drive > to re-order commands

FUA and TCQ (was: Plan: journalling fixes for WAPBL)

2016-09-23 Thread Edgar Fuß
> The whole point of tagged queueing is to let you *not* set [the write > cache] bit in the mode pages and still get good performance. I don't get that. My understanding was that TCQ allowed the drive to re-order commands within the bounds described by the tags. With the write cache disabled,