BFS 453/454/455/456 and 3.16-ck2

Here is an updated set of BFS patches with the accumulated bugfixes as debugged on this blog for kernels 3.13 to 3.16 inclusive. The main obvious bug which affected people was the ath9k module which would hang on suspend/resume. However there were likely a number of subtle bugs across the board that most people would not be aware of and even I only noticed that kvm behaved much better after this applied bugfix which stretches back to every BFS after 3.12.

In order to make up for the fact that there are numerous kernels out there based on BFS across the different versions, I have updated BFS and numbered the versions according to which base kernel they are on. Note that there are no feature backports on the older kernels, only the bugfixes, so SMT nice is only on the 3.16 BFS.

3.13-sched-bfs-453.patch
3.14-sched-bfs-454.patch
3.15-sched-bfs-455.patch
3.16-sched-bfs-456.patch

And along with that an updated ck branded release for 3.16, 3.16-ck2:

3.16-ck2


Enjoy!
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SMT Nice 6

In my last post I discussed the problem with nice levels, scheduling policies and SMT, and my first public patch for BFS to work around the issue, "SMT Nice":

smthyperthreading-nice-and-scheduling.html

With a bit of extra testing, and feedback from a number of users, a few issues were discovered with the first patch, so I've reworked it. Thanks very much to those who tested it and provided feedback. There were a couple of scheduling points where SMT siblings weren't being examined, and the difference between nice levels was far more aggressive than it was supposed to be.

Here is an updated patch for BFS 449 with all pending patches:
bfs449-smtnice-6.patch

And a convenient all inclusive patch for 3.15 with ck1+pending+smtnice3456:
3.15-ck1-smtnice6.patch

EDIT: Added one minor change to not allow kernel threads to deschedule any users tasks on smt siblings and bumped the patch version up to smtnice4.

EDIT2: Added a change to fix the high power usage bug bringing version up to smtnice5

EDIT3: Fixed a logic fail which would cause far too many reschedules and not use full CPU with many niced tasks bringing the version up to smtnice6.

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Enjoy!
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-ck

BFS 0.449

Hot on the heels of the BFS448 release, I was doing some experimenting for some ideas I had (nothing productive so far) when I discovered the long-standing "CPU locality" code which determines the relationship between CPUs (eg. if they're SMT siblings or separate physical CPUs etc) was broken. So I've fixed the code that determines that, along with printing out what BFS believes to be the relationship (called locality) in dmesg on startup. An example output from a 2 thread, 2 core CPU would be:

[ 0.100217] LOCALITY CPU 0 to 1: 1
[ 0.100220] LOCALITY CPU 0 to 2: 2
[ 0.100221] LOCALITY CPU 0 to 3: 2
[ 0.100222] LOCALITY CPU 1 to 2: 2
[ 0.100223] LOCALITY CPU 1 to 3: 2
[ 0.100224] LOCALITY CPU 2 to 3: 1

I've also added the namespace fix as posted by here by Bogdan Trach (Thanks!). Diff from BFS 0.448 and full patch here:

BFS 3.15 patches

The changes in this patch may improve CPU throughput and decrease latency under certain circumstances but no benchmarking so far has shown any statistically significant difference.

Enjoy!

BFS 0.448, 3.15-ck1

Announcing a resync and update of BFS for linux kernel 3.15.x. I'm currently on vacation but fortunately had enough downtime to hack this together in the evenings and pinged a few people to do some testing for me before releasing it since I only have my laptop with me and could not do the usual set of build and run tests on multiple configurations (thanks!).

 This is basically a resync of the last BFS along with trivial changes to stay in sync with the mainline kernel, along with some of the queued build fixes submitted by others on this blog (thanks!). Alas the users of ath9k with Tux On Ice that I pinged early on with a test patch have shown the same issue exists (which is not surprising since BFS has only been trivially changed in quite a few releases now) so I'm pretty sure whatever the interaction is was introduced somewhere between 3.13 and 3.14.

I have reviewed Alfred Chen's patches and for the time being have not included them in BFS, though I do like the direction his changes have taken. The first patch sets a flag that isn't used by BFS so it was not necessary. The other changes to resched_best_mask are sound and the only thing they're missing is an equivalent optimisation for compiled in support for MC and SMT schedulers on hardware that doesn't have one and/or the other.

 So here it is:

BFS by itself:

3.15-sched-bfs-448.patch

3.15-ck1 patchset directory:

3.15-ck1

Enjoy!

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