Friday, 4 July 2014

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.


Thursday, 3 July 2014

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-ck1 patchset directory:


Tuesday, 6 May 2014

BFS 0.447, 3.14-ck1

Announcing a resync and update of BFS for linux kernel 3.14.x:

This is mainly a resync from BFS 0.446, but with the addition of the patches as offered by the generous users as seen in the comments here, Alfred Chen and Oleksandr Natalenko. The changes are to fix a circular locking issue on bootup that rarely hit some people, a fix for kvm soft lockups in SMP mode, and to remove some config options that should not be used with BFS.
What's interesting about working on this latest BFS is that I ran into all sorts of instability due to the new kernel that ironically worked out to be a very serious bug in 3.14.0 and was fixed in 3.14.1 with this patch:
commit 8e58cd80d042569da7af501de897c5e0538d99b0
futex: avoid race between requeue and wake
As is often the case, BFS is exceptional at bringing out race conditions and my machine was almost unusable with any significantly multithreaded application such as firefox which kept hanging. This was a scenario where my delay at syncing up the code worked to my advantage as 3.14.2 is working fine.
So here it is:
BFS by itself:

CK branded BFS:

Somehow I still forgot to include PF's patch for uniprocessor builds, though it's so uncommon to come across a uniprocessor these days! His patch is still valid and can be grabbed here to be applied on top if you need it:



Monday, 3 March 2014

BFS 0.446, 3.13-ck1

Announcing a resync and update of BFS for linux kernel 3.13.x:

Apart from build fixes and synchronisation with new kernel changes, this is only trivially different to BFS 444. A build failure on 445, along with a desire to release only even numbers, prompted version 446.

BFS by itself:

CK branded BFS:

Apologies for the delay, but I simply swamped with my other projects, interests and work.