On Thu, Feb 20, 2020 at 04:52:47AM +0800, Alex Williamson wrote: > On Wed, 19 Feb 2020 04:04:17 -0500 > Yan Zhao <yan.y.zhao@xxxxxxxxx> wrote: > > > On Fri, Jan 17, 2020 at 09:10:51AM +0800, Yan Zhao wrote: > > > Thank you, Alex! > > > I'll try it and let you know the result soon. :) > > > > > > On Fri, Jan 17, 2020 at 02:17:49AM +0800, Alex Williamson wrote: > > > > Hi Yan, > > > > > > > > I wonder if this might reduce the lock contention you're seeing in the > > > > vfio_dma_rw series. These are only compile tested on my end, so I hope > > > > they're not too broken to test. Thanks, > > > > > > > > Alex > > > > > > > > --- > > > > > > > > Alex Williamson (3): > > > > vfio/type1: Convert vfio_iommu.lock from mutex to rwsem > > > > vfio/type1: Replace obvious read lock instances > > > > vfio/type1: Introduce pfn_list mutex > > > > > > > > > > > > drivers/vfio/vfio_iommu_type1.c | 67 ++++++++++++++++++++++++--------------- > > > > 1 file changed, 41 insertions(+), 26 deletions(-) > > > > > > > > hi Alex > > I have finished testing of this series. > > It's quite stable and passed our MTBF testing :) > > > > However, after comparing the performance data obtained from several > > benchmarks in guests (see below), > > it seems that this series does not bring in obvious benefit. > > (at least to cases we have tested, and though I cannot fully explain it yet). > > So, do you think it's good for me not to include this series into my next > > version of "use vfio_dma_rw to read/write IOVAs from CPU side"? > > Yes, I would not include it in your series. No reason to bloat your > series for a feature that doesn't clearly show an improvement. Thanks > for the additional testing, we can revive them if this lock ever > resurfaces. I'm was actually more hopeful that holding an external > group reference might provide a better performance improvement, the > lookup on every vfio_dma_rw is not very efficient. Thanks, > got it. thanks~ Yan
