On Thu, Aug 04, 2016 at 10:40:35AM +0530, Srikar Dronamraju wrote: > * Dave Hansen <dave.hansen@xxxxxxxxx> [2016-08-03 12:40:17]: > > > On 08/02/2016 11:35 PM, Srikar Dronamraju wrote: > > > On a regular kernel with CONFIG_FADUMP and fadump configured, 5% of the > > > total memory is reserved for booting the kernel on crash. On crash, > > > fadump kernel reserves the 95% memory and boots into the 5% memory that > > > was reserved for it. It then parses the reserved 95% memory to collect > > > the dump. > > > > > > The problem is not about the amount of memory thats reserved for fadump > > > kernel. Even if we increase/decrease, we will still end up with the same > > > issue. > > > > Oh, and the dentry/inode caches are sized based on 100% of memory, not > > the 5% that's left after the fadump reservation? > > Yes, the dentry/inode caches are sized based on the 100% memory. > By and large, I'm not a major fan of introducing an API to disable it for a single feature that is arch-specific because it's very heavy handed. There is no guarantee that the existence of fadump will cause a failure If fadump is reserving memory and alloc_large_system_hash(HASH_EARLY) does not know about then then would an arch-specific callback for arch_reserved_kernel_pages() be more appropriate? fadump would need to return how many pages it reserved there. That would shrink the size of the inode and dentry hash tables when booting with 95% of memory reserved. That approach would limit the impact to ppc64 and would be less costly than doing a memblock walk instead of using nr_kernel_pages for everyone else. > > Is the deferred initialization kicked in progress at the time we do the > > dentry/inode allocations? Can waiting a bit let the allocation succeed? > > > > Right now deferred initialisation kicks in after dentry/inode > allocations. > > Can we defer the cache allocations till deferred > initialisation? I dont know. Only by backing it with vmalloc memory. -- Mel Gorman SUSE Labs -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>