On 06/22/2011 01:30 PM, Stefan Assmann wrote: > On 22.06.2011 20:15, H. Peter Anvin wrote: >> On 06/22/2011 04:18 AM, Stefan Assmann wrote: >>> >>> The idea is to allow the user to specify RAM addresses that shouldn't be >>> touched by the OS, because they are broken in some way. Not all machines have >>> hardware support for hwpoison, ECC RAM, etc, so here's a solution that allows to >>> use bitmasks to mask address patterns with the new "badram" kernel command line >>> parameter. >>> Memtest86 has an option to generate these patterns since v2.3 so the only thing >>> for the user to do should be: >>> - run Memtest86 >>> - note down the pattern >>> - add badram=<pattern> to the kernel command line >>> >> >> We already support the equivalent functionality with >> memmap=<address>$<length> for those with only a few ranges... this has >> been supported for ages, literally. For those with a lot of ranges, >> like Google, the command line is insufficient. > > Right, I think this has been discussed a while ago. So the advantages I > see in this approach are. It allows to break down memory exclusion to > the page level with a pattern of non-consecutive pages. So if every > other page would be considered bad that's a bit tough to deal with using > memmap. > Secondly patterns can be easily generated by running Memtest86 and thus > easily be fed to the kernel by command line. Making it much more feasible > for the average user to take advantage of it. > How common are nontrivial patterns on real hardware? This would be interesting to hear from Google or another large user. If so, we should probably introduce this as another linked-list data structure; we can allow it to be preprocessed from the command line if need be. I have to say I think Google's point that truncating the list is unacceptable... that would mean running in a known-bad configuration, and even a hard crash would be better. -hpa -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>