Hi, On 12/03/14 at 11:35am, Joerg Roedel wrote: > Hi, > > On Wed, Dec 03, 2014 at 12:01:23PM +0800, WANG Chao wrote: > >From your experience It seems like swiotlb isn't working well with > > crashkernel=X,high alone. What about using crashkernel=X,low with > > crashkernel=X,high? Is there any reason you have to use > > crashkernel=X,high alone? > > Sure, when I specify an additional crashkernel=X,low then I can get > things to work this way too. But my patch-set is about changing the > default, since the failure was seen on common server systems with the > defaults.
crashkernel=X doesn't work for you? > > > crashkernel=X,high shouldn't automatically reserve 72M low at the first > > place. Now it's going insane if you increase it to 256M by default. > > How should a kernel without some low memory (which has only memory above > 4G available) handle any 32bit DMA devices? There would be no way to > allocate DMA-able memory for those devices. I mean crashkernel=X,high shouldn't automatically reserve low. crashkernel=X,high should always be used together with crashkernel=X,low. If one is not satisfied with the combination of two parameters, crashkernel=X should be able to look for a suitable area below 4G. But right now, crashkernel=X only deals under 896M. I've sent a patch for this in the past: [PATCH] x86, kdump: crashkernel=X try to reserve below 896M first, then try below 4G, then MAXMEM - https://lkml.org/lkml/2013/10/14/183 X86 people don't like this idea so I didn't update the patch even there's minor nit to clean up. > > And as I said, if people prefer it I can change the patch-set so that > the amount of low-memory allocated is subtracted from the amount of > high-memory. This way the overall memory usage for kdump would stay the > same while changing the defaults to work on more systems. Say you do this, crashkernel=X,high would be reserve (X-n) high and (n) low? IMHO I think it's better crashkernel=X,high means reserve X high and high only. Thanks WANG Chao -- 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/
