On Wed, Jan 15, 2014 at 1:31 PM, Dan Williams <dan.j.willi...@intel.com> wrote: > On Wed, Jan 15, 2014 at 1:20 PM, saeed bishara <saeed.bish...@gmail.com> > wrote: >> Hi Dan, >> >> I'm using net_dma on my system and I achieve meaningful performance >> boost when running Iperf receive. >> >> As far as I know the net_dma is used by many embedded systems out >> there and might effect their performance. >> Can you please elaborate on the exact scenario that cause the memory >> corruption? >> >> Is the scenario mentioned here caused by "real life" application or >> this is more of theoretical issue found through manual testing, I was >> trying to find the thread describing the failing scenario and couldn't >> find it, any pointer will be appreciated. > > Did you see the referenced commit? > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=77873803363c > > This is a real issue in that any app that forks() while receiving data > can cause the dma data to be lost. The problem is that the copy > operation falls back to cpu at many locations. Any one of those > instance could touch a mapped page and trigger a copy-on-write event. > The dma completes to the wrong location. >
Btw, do you have benchmark data showing that NET_DMA is beneficial on these platforms? I would have expected worse performance on platforms without i/o coherent caches. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
