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Date: Wed, 29 Mar 2017 09:10:56 -0700 From: Davidlohr Bueso <dave@...olabs.net> To: "Kirill A. Shutemov" <kirill@...temov.name> Cc: Laurent Dufour <ldufour@...ux.vnet.ibm.com>, mingo@...nel.org, peterz@...radead.org, akpm@...ux-foundation.org, jack@...e.cz, kirill.shutemov@...ux.intel.com, mhocko@...e.com, mgorman@...hsingularity.net, linux-kernel@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de> Subject: Re: [PATCH 1/5] locking: Introduce range reader/writer lock On Wed, 29 Mar 2017, Kirill A. Shutemov wrote: >On Wed, Mar 29, 2017 at 08:31:33AM -0700, Davidlohr Bueso wrote: >> On Wed, 29 Mar 2017, Laurent Dufour wrote: >> >> > On 28/03/2017 18:58, Kirill A. Shutemov wrote: >> > > On Tue, Mar 28, 2017 at 09:39:18AM -0700, Davidlohr Bueso wrote: >> > > > I'll wait to see if there are any more concerns and send a v2 with your corrections. >> > > >> > > Have you tried drop-in replacement of mmap_sem with full range lock? >> > > It would be interesting to see performance implication for this. >> > > >> > >> > I've a patch that replace the mmap_sem with a full range lock, it seems >> > to work fine for x86 and ppc64 for now. I'll send it soon. >> > But I didn't yet check for performance. What is the best way to that ? >> >> I expect performance to take a measurable hit if we simply use full range >> lock as a drop in replacement. My rwsem vs range lock measurements were >> done with this in mind. We only win with range locks when improving the >> level of parallelism. > >It would be hard sell if we would see performance degradation simple >single-threaded workload. Yeah, that's why I included very low contention in the lock comparison. Deltas are very much within the noise region, it is with high contention where things go south performance wise.
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