On 09/07/23 at 11:39am, Uladzislau Rezki wrote: > On Thu, Sep 07, 2023 at 10:17:39AM +0800, Baoquan He wrote: > > Add Kazu and Lianbo to CC, and kexec mailing list > > > > On 08/29/23 at 10:11am, Uladzislau Rezki (Sony) wrote: > > > Store allocated objects in a separate nodes. A va->va_start > > > address is converted into a correct node where it should > > > be placed and resided. An addr_to_node() function is used > > > to do a proper address conversion to determine a node that > > > contains a VA. > > > > > > Such approach balances VAs across nodes as a result an access > > > becomes scalable. Number of nodes in a system depends on number > > > of CPUs divided by two. The density factor in this case is 1/2. > > > > > > Please note: > > > > > > 1. As of now allocated VAs are bound to a node-0. It means the > > > patch does not give any difference comparing with a current > > > behavior; > > > > > > 2. The global vmap_area_lock, vmap_area_root are removed as there > > > is no need in it anymore. The vmap_area_list is still kept and > > > is _empty_. It is exported for a kexec only; > > > > I haven't taken a test, while accessing all nodes' busy tree to get > > va of the lowest address could severely impact kcore reading efficiency > > on system with many vmap nodes. People doing live debugging via > > /proc/kcore will get a little surprise. > > > > > > Empty vmap_area_list will break makedumpfile utility, Crash utility > > could be impactd too. I checked makedumpfile code, it relys on > > vmap_area_list to deduce the vmalloc_start value. > > > It is left part and i hope i fix it in v3. The problem here is > we can not give an opportunity to access to vmap internals from > outside. This is just not correct, i.e. you are not allowed to > access the list directly.
Right. Thanks for the fix in v3, that is a relief of makedumpfile and crash. Hi Kazu, Meanwhile, I am thinking if we should evaluate the necessity of vmap_area_list in makedumpfile and Crash. In makedumpfile, we just use vmap_area_list to deduce VMALLOC_START. Wondering if we can export VMALLOC_START directly. Surely, the lowest va->va_start in vmap_area_list is a tighter low boundary of vmalloc area and can reduce unnecessary scanning below the lowest va. Not sure if this is the reason people decided to export vmap_area_list. Thanks Baoquan _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec
