On Tue, 25 Mar 2014 01:14:21 +0000 Atsushi Kumagai <kumagai-atsushi at mxc.nes.nec.co.jp> wrote: [snip] > >But it looks like get_mm_sparsemem() does not check for zero. > >The nr_to_section() function just returns an invalid address > >(something between 0 and 4096) for section in case we get zero > >from the "mem_section" entry. This is address is then used for > >calculating "mem_map": > > In other architectures, the check by is_kaddr() avoids to > read invalid address, but it doesn't do anything in the case > of s390 due to the its memory management mechanism: > > s390x: Fix KVBASE to correct value for s390x architecture. > http://lists.infradead.org/pipermail/kexec/2011-March/004930.html Right, for s390 the zero page is valid. > Finally I've understood the cause of this issue completely, > thanks for your report. > > >mem_map = section_mem_map_addr(section); > >mem_map = sparse_decode_mem_map(mem_map, section_nr); > > > >With the patch below I could use makedumpfile (1.5.3) successfully > >on the 1TB dump with mem=1G. I attached the -D output that is > >created by makedumpfile with the patch. > > > >But compared to my first patch it takes much longer and the resulting > >dump is bigger (version 1.5.3): > > > > | Dump time | Dump size > >-------------+-------------+----------- > >First patch | 10 sec | 124 MB > >Second patch | 87 minutes | 6348 MB > > > >No idea why the dump is bigger with the second patch. I think the time > >is consumed in write_kdump_pages_cyclic() by checking for zero pages > >for the whole range: > > I suppose this difference was resolved with the v2 of the second patch, > right? Right, with the last patch the dump time and size were ok. [snip] > >So the first patch would be better for my scenario. What in particular are your > >concerns with that patch? > > I think the v2 second patch is a reasonable patch to fix the > bug of get_mm_sparsemem(). > Additionally, the latest patch you posted to adjust max_mapnr > (which using mem_map_data[]) is acceptable instead of the first > patch. > So could you re-post the two as a formal patch set? > I mean patch descriptions and your signature are needed. Ok great! I will resend the patches. Michael
