Jens Axboe <axboe@xxxxxxxxx> writes:>
On 2014-05-30 00:10, Rusty Russell wrote:
Jens Axboe <axboe@xxxxxxxxx> writes:
If Rusty agrees, I'd like to add it for 3.16 with a stable marker.
Really stable? It improves performance, which is nice. But every patch
which goes into the kernel fixes a bug, improves clarity, improves
performance or adds a feature. I've now seen all four cases get CC'd
into stable.
Including some of mine explicitly not marked stable which get swept up
by enthusiastic stable maintainers :(
Is now there *any* patch short of a major rewrite which shouldn't get
cc: stable?
I agree that there's sometimes an unfortunate trend there. I didn't
check, but my assumption was that this is a regression after the blk-mq
conversion, in which case I do think it belongs in stable.
No, it's always been that way. In the original driver the entire "issue
requests" function was under the lock.
But in any case, I think the patch is obviously correct and the wins are
sufficiently large to warrant a stable inclusion even if it isn't a
regression.
If you're running SMP under an emulator where exits are expensive, then
this wins. Under KVM it's marginal at best.
Locking changes which are "obviously correct" make me nervous, too :)
But IIRC last KS the argument is that not *enough* is going into stable,
not that stable isn't stable enough. So maybe it's a non-problem?