On Mon, Oct 14, 2024 at 09:41:51AM +0200, Christoph Hellwig wrote: > On Mon, Oct 14, 2024 at 09:23:14AM +0200, Hannes Reinecke wrote: > >> 3) some storage utilities > >> - dm thin provisioning utility of thin_check > >> - `dt`(https://github.com/RobinTMiller/dt) > >> > >> I looks like same user buffer is used in more than 1 dio. > >> > >> 4) some self cooked test code which does same thing with 1) > >> > >> In storage stack, the buffer provider is far away from the actual DMA > >> controller operating code, which doesn't have the knowledge if > >> DMA_ATTR_SKIP_CPU_SYNC should be set. > >> > >> And suggestions for avoiding this noise? > >> > > Can you check if this is the NULL page? Operations like 'discard' will > > create bios with several bvecs all pointing to the same NULL page. > > That would be the most obvious culprit. > > The only case I fully understand without looking into the details > is raid1, and that will obviously map the same data multiple times The other cases should be concurrent DIOs on same userspace buffer. Thanks, Ming
