search for: multicopi

On Wed, Jan 02, 2019 at 03:57:58PM -0500, Michael S. Tsirkin wrote: > @@ -875,6 +893,8 @@ to the CPU containing it. See the section on "Multicopy atomicity" > for more information. > > > + > + > In summary: > > (*) Control dependencies can order prior loads against later stores. Was this hunk intentional?

On 2019/1/3 ??4:57, Michael S. Tsirkin wrote: > It's not uncommon to have two access two unrelated memory locations in a > specific order. At the moment one has to use a memory barrier for this. > > However, if the first access was a read and the second used an address > depending on the first one we would have a data dependency and no > barrier would be necessary. > >

On 2019/1/3 ??4:57, Michael S. Tsirkin wrote: > It's not uncommon to have two access two unrelated memory locations in a > specific order. At the moment one has to use a memory barrier for this. > > However, if the first access was a read and the second used an address > depending on the first one we would have a data dependency and no > barrier would be necessary. > >

So as explained in Documentation/memory-barriers.txt e.g. a load followed by a store require a full memory barrier, to avoid store being ordered before the load. Similarly load-load requires a read memory barrier. Thinking about it, we can actually create a data dependency by mixing the first loaded value into the pointer being accessed. This adds an API for this and uses it in virtio. Written

2009/11/8 Chris Lattner <clattner at apple.com>: > The first step is loop dependence analysis.  This is required to determine > loop reuse information and is the basis for a lot of vectorization and > parallelization loop transformations. I suppose all dependencies can be determined with function passes and module-wide analysis. LLVM does unroll small loops, but once the number of

On Nov 7, 2009, at 4:15 PM, Renato Golin wrote: > 2009/11/7 Chris Lattner <clattner at apple.com>: >> I enjoyed this presentation: >> http://www.linux-kongress.org/2009/slides/compiler_survey_felix_von_leitner.pdf > > Wow, very comprehensive! > > Is there anyone working on vectorization? This is something that > interests me, I might give it a try, just need

It's not uncommon to have two access two unrelated memory locations in a specific order. At the moment one has to use a memory barrier for this. However, if the first access was a read and the second used an address depending on the first one we would have a data dependency and no barrier would be necessary. This adds a new interface: dependent_ptr_mb which does exactly this: it returns a

On Mon, Jan 07, 2019 at 11:58:23AM +0800, Jason Wang wrote: > > On 2019/1/3 ??4:57, Michael S. Tsirkin wrote: > > It's not uncommon to have two access two unrelated memory locations in a > > specific order. At the moment one has to use a memory barrier for this. > > > > However, if the first access was a read and the second used an address > > depending