[lkml]   [2003]   [Feb]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: stochastic fair queueing in the elevator [Re: [BENCHMARK] 2.4.20-ck3 / aa / rmap with contest]
David Lang <> wrote:
> note that issuing a fsync should change all pending writes to 'syncronous'
> as should writes to any partition mounted with the sync option, or writes
> to a directory with the S flag set.

We know, at I/O submission time, whether a write is to be waited upon.
That's in writeback_control.sync_mode.

That, combined with an assumption that "all reads are synchronous" would
allow the outgoing BIOs to be appropriately tagged.

It's still approximate. An exact solution would involve only marking I/O as
synchronous when some process actually waits on its completion. I do not
believe that all the extra lookup and locking infrastructure and storage
which this would require is justified. Certainly not in a first iteration.

The Rice Uni researchers did implement controls which attempted to learn IO
submission patterns on a per-process basis, and I believe these were also
used to avoid undesirable starvations. We have only briefly played with
process-aware logic.

The first thing to do is to get the anticipatory scheduler working properly.
Nick has been tied down for a week chasing generic bugs in the request layer.
He seems to have nailed the important ones now.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 13:33    [W:0.087 / U:0.784 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site