Messages in this thread | | | Subject | Re: [RFC][PATCH 0/3] Skip I/O merges when disabled | From | Andi Kleen <> | Date | Thu, 24 Apr 2008 15:29:05 +0200 |
| |
"Alan D. Brunelle" <Alan.Brunelle@hp.com> writes:
> The block I/O + elevator + I/O scheduler code spends a lot of time > trying to merge I/Os -- rightfully so under "normal" circumstances. > However, if one were to know that the incoming I/O stream was /very/ > random in nature, the cycles are wasted. (This can be the case, for > example, during OLTP-type runs.) > > This patch stream adds a per-request_queue tunable that (when set) > disables merge attempts, thus freeing up a non-trivial amount of CPU cycles.
It sounds interesting. But explicit tunables are always bad because they will be only used by a elite few. Do you think it would be possible instead to keep some statistics on how successfull merging is and when the success rate is very low disable it automatically for some time until a time out?
This way nearly everybody could get most of the benefit from this change.
-Andi
| |