[zfs-code] Read reordering

2010-01-11 Thread Andrey Kuzmin
On Mon, Jan 11, 2010 at 10:30 PM, Richard Elling wrote: > I misinterpreted the question. My answer assumes reads from the same file. > > AFAIK, there is no thread-level I/O scheduler in Solaris. ZFS uses a priority > scheduler which is based on the type of I/O and there are some other > resource m

[zfs-code] Read reordering

2010-01-11 Thread Andrey Kuzmin
On Mon, Jan 11, 2010 at 9:29 PM, bank kus wrote: >> Then you're actually asking for a fair I/O scheduler. > > yes are we currently fair? any good documentation on the priority model as it > exists today? I doubt it, first come-first go is most common. The same holds for memory as well. Regards,

[zfs-code] Read reordering

2010-01-11 Thread Andrey Kuzmin
Then you're actually asking for a fair I/O scheduler. Regards, Andrey On Mon, Jan 11, 2010 at 8:12 PM, bank kus wrote: > I was asking from the starvatoin point of view to see if B can be starved by > a long bust from A > -- > This message posted from opensolaris.org > ___

[zfs-code] Read reordering

2010-01-11 Thread bank kus
> resource management policies implemented. By default, > ZFS will queue > 35 I/Os to each leaf vdev, so it is not clear that > scheduling above the ZFS > level will be as effective It doesnt have to be above the _ZFS_ layer no? In place of a single queue one could maintain separate queues that

[zfs-code] Read reordering

2010-01-11 Thread Andrey Kuzmin
Per Posix there's no read ordering guarantees for a file with concurrent non-exclusive readers. Use queue/locks in the application if you need ordering like this. Regards, Andrey On Mon, Jan 11, 2010 at 7:05 PM, bank kus wrote: > As of 2009.06 what is the policy with reordering ZFS file reads

[zfs-code] Read reordering

2010-01-11 Thread Richard Elling
On Jan 11, 2010, at 11:41 AM, Andrey Kuzmin wrote: > On Mon, Jan 11, 2010 at 10:30 PM, Richard Elling > wrote: >> I misinterpreted the question. My answer assumes reads from the same file. >> >> AFAIK, there is no thread-level I/O scheduler in Solaris. ZFS uses a priority >> scheduler which is b

[zfs-code] Read reordering

2010-01-11 Thread Richard Elling
I misinterpreted the question. My answer assumes reads from the same file. AFAIK, there is no thread-level I/O scheduler in Solaris. ZFS uses a priority scheduler which is based on the type of I/O and there are some other resource management policies implemented. By default, ZFS will queue 35 I/Os

[zfs-code] Read reordering

2010-01-11 Thread Richard Elling
On Jan 11, 2010, at 8:05 AM, bank kus wrote: > As of 2009.06 what is the policy with reordering ZFS file reads i.e., > consider the following timeline: > T0: Process A issues read of size 20K and gets its thread switched out > > T1: Process B issues reads of size 8 bytes and gets its thread sw

[zfs-code] Read reordering

2010-01-11 Thread bank kus
> I doubt it, first come-first go is most common. The > same holds for > memory as well. > Regards, > Andrey and that is because it was considered and rejected because of XYZ reaons (or lack of sufficient reasons) or simply something thats not been evaluated. I would argue the following problem

[zfs-code] Read reordering

2010-01-11 Thread bank kus
> Then you're actually asking for a fair I/O scheduler. yes are we currently fair? any good documentation on the priority model as it exists today? -- This message posted from opensolaris.org

[zfs-code] Read reordering

2010-01-11 Thread bank kus
I was asking from the starvatoin point of view to see if B can be starved by a long bust from A -- This message posted from opensolaris.org

[zfs-code] Read reordering

2010-01-11 Thread bank kus
As of 2009.06 what is the policy with reordering ZFS file reads i.e., consider the following timeline: T0: Process A issues read of size 20K and gets its thread switched out T1: Process B issues reads of size 8 bytes and gets its thread switched out Are the 8 byte reads from B going to fall in