On 28/11/2023 4:34 pm, Andy Shevchenko wrote:
On Tue, Nov 28, 2023 at 6:31 PM Robin Murphy <robin.murphy@xxxxxxx> wrote:
On 28/11/2023 3:18 pm, Alan Stern wrote:
On Tue, Nov 28, 2023 at 02:37:02PM +0100, Christoph Hellwig wrote:
...
The logical confcusion from that would be that IFF dma-debug is enabled on
any platform we need to set ARCH_DMA_MINALIGN to the cache line size.
(IF, not IFF.) And tell distributions that CONFIG_DMA_API_DEBUG is not
meant for production systems but rather for kernel testing, right?
Yikes, I'd hope that distros are heeding the warning that the Kconfig
calls out already. It's perhaps somewhat understated, as I'd describe
the performance impact to large modern systems with high-bandwidth I/O
as somewhere between "severe" and "crippling".
Independently on the distros configurations the (false positive)
message(s) will make difficult to debug the actual things, shouldn't
we have our code robust in any case?
Sure, I have no objection to making dma-debug more robust and useful for
its intended purpose, I was just commenting on the fact that any
potential change in behaviour from this should be of less concern to
distros than the significant change in behaviour that enabling it
*already* poses (i.e. globally serialising DMA operations and doing
inherently slow stuff in what are normally expected to be fast paths).
Thanks,
Robin.
