[dm-devel] A patchset to limit the number of outstanding bios
Joe Thornber
thornber at redhat.com
Mon Oct 13 16:03:18 UTC 2014
On Mon, Oct 13, 2014 at 11:27:20AM -0400, Mikulas Patocka wrote:
> Hi
>
> I'm announcing the release of a patchset that limits the number of
> outstanding bios in the device mapper.
Interesting; Mike and I were considering this for throttling io to
thinp a couple of weeks ago. The reason we didn't go with this was,
for thinp, there are cheap bios (eg, a quick remap) and expensive bios
(eg, one that triggers a copy on write exception). This means it's
very hard to come up with a single number that represents too many
bios. Instead I throttle by looking at how long it's taking the
worker thread to get through it's work queue.
Could you make this limit optional please? eg, setting the limit to 0
turns it off, and I'd prefer a default of 0/off.
- Joe
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