On Thu, Jan 28, 2021 at 08:29:57AM +0100, Alexander Sverdlin wrote:
> Hi!
>
> On 27/01/2021 23:34, Peter Zijlstra wrote:
> > On Wed, Jan 27, 2021 at 09:36:24PM +0100, Alexander A Sverdlin wrote:
> >> From: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
> >>
> >> Flushing the write buffer brings aroung 10% performace on the tight
> >> uncontended spinlock loops on Octeon. Refer to commit 500c2e1fdbcc
> >> ("MIPS: Optimize spinlocks.").
> > No objection to the patch, but I don't find the above referenced commit
> > to be enlightening wrt nudge_writes(). The best it has to offer is the
> > comment that's already in the code.
>
> My point was that original MIPS spinlocks had this write-buffer-flush and
> it got lost on the conversion to qspinlocks. The referenced commit just
> allows to see the last MIPS-specific implementation before deletion.
Hardware that needs a store-buffer flush after release is highly suspect
and needs big and explicit comments. Not vague hints.
