Hello David! I have checked you series with 1G hugepage, but only in 1 Gbit/sec network environment. I started Ubuntu just with console interface and gave to it only 1G of RAM, inside Ubuntu I started stress command (stress --cpu 4 --io 4 --vm 4 --vm-bytes 256000000 &) in such environment precopy live migration was impossible, it never being finished, in this case it infinitely sends pages (it looks like dpkg scenario).
Also I modified stress utility http://people.seas.harvard.edu/~apw/stress/stress-1.0.4.tar.gz due to it wrote into memory every time the same value `Z`. My modified version writes every allocation new incremented value. I'm using Arcangeli's kernel only at the destination. I got controversial results. Downtime for 1G hugepage is close to 2Mb hugepage and it took around 7 ms (in 2Mb hugepage scenario downtime was around 8 ms). I made that opinion by query-migrate. {"return": {"status": "completed", "setup-time": 6, "downtime": 6, "total-time": 9668, "ram": {"total": 1091379200, "postcopy-requests": 1, "dirty-sync-count": 2, "remaining": 0, "mbps": 879.786851, "transferred": 1063007296, "duplicate": 7449, "dirty-pages-rate": 0, "skipped": 0, "normal-bytes": 1060868096, "normal": 259001}}} Documentation says about downtime field - measurement unit is ms. So I traced it (I added additional trace into postcopy_place_page trace_postcopy_place_page_start(host, from, pagesize); ) postcopy_ram_fault_thread_request Request for HVA=7f6dc0000000 rb=/objects/mem offset=0 postcopy_place_page_start host=0x7f6dc0000000 from=0x7f6d70000000, pagesize=40000000 postcopy_place_page_start host=0x7f6e0e800000 from=0x55b665969619, pagesize=1000 postcopy_place_page_start host=0x7f6e0e801000 from=0x55b6659684e8, pagesize=1000 several pages with 4Kb step ... postcopy_place_page_start host=0x7f6e0e817000 from=0x55b6659694f0, pagesize=1000 4K pages, started from 0x7f6e0e800000 address it's vga.ram, /rom@etc/acpi/tables etc. Frankly saying, right now, I don't have any ideas why hugepage wasn't resent. Maybe my expectation of it is wrong as well as understanding ) stress utility also duplicated for me value into appropriate file: sec_since_epoch.microsec:value 1487003192.728493:22 1487003197.335362:23 *1487003213.367260:24* *1487003238.480379:25* 1487003243.315299:26 1487003250.775721:27 1487003255.473792:28 It mean rewriting 256Mb of memory per byte took around 5 sec, but at the moment of migration it took 25 sec. Another one request. QEMU could use mem_path in hugefs with share key simultaneously (-object memory-backend-file,id=mem,size=${mem_size},mem-path=${mem_path},share=on) and vm in this case will start and will properly work (it will allocate memory with mmap), but in case of destination for postcopy live migration UFFDIO_COPY ioctl will fail for such region, in Arcangeli's git tree there is such prevent check (if (!vma_is_shmem(dst_vma) && dst_vma->vm_flags & VM_SHARED). Is it possible to handle such situation at qemu? On Mon, Feb 06, 2017 at 05:45:30PM +0000, Dr. David Alan Gilbert wrote: > * Dr. David Alan Gilbert (git) (dgilb...@redhat.com) wrote: > > From: "Dr. David Alan Gilbert" <dgilb...@redhat.com> > > > > Hi, > > The existing postcopy code, and the userfault kernel > > code that supports it, only works for normal anonymous memory. > > Kernel support for userfault on hugetlbfs is working > > it's way upstream; it's in the linux-mm tree, > > You can get a version at: > > git://git.kernel.org/pub/scm/linux/kernel/git/andrea/aa.git > > on the origin/userfault branch. > > > > Note that while this code supports arbitrary sized hugepages, > > it doesn't make sense with pages above the few-MB region, > > so while 2MB is fine, 1GB is probably a bad idea; > > this code waits for and transmits whole huge pages, and a > > 1GB page would take about 1 second to transfer over a 10Gbps > > link - which is way too long to pause the destination for. > > > > Dave > > Oops I missed the v2 changes from the message: > > v2 > Flip ram-size summary word/compare individual page size patches around > Individual page size comparison is done in ram_load if 'advise' has been > received rather than checking migrate_postcopy_ram() > Moved discard code into exec.c, reworked ram_discard_range > > Dave Thank your, right now it's not necessary to set postcopy-ram capability on destination machine. > > > Dr. David Alan Gilbert (16): > > postcopy: Transmit ram size summary word > > postcopy: Transmit and compare individual page sizes > > postcopy: Chunk discards for hugepages > > exec: ram_block_discard_range > > postcopy: enhance ram_block_discard_range for hugepages > > Fold postcopy_ram_discard_range into ram_discard_range > > postcopy: Record largest page size > > postcopy: Plumb pagesize down into place helpers > > postcopy: Use temporary for placing zero huge pages > > postcopy: Load huge pages in one go > > postcopy: Mask fault addresses to huge page boundary > > postcopy: Send whole huge pages > > postcopy: Allow hugepages > > postcopy: Update userfaultfd.h header > > postcopy: Check for userfault+hugepage feature > > postcopy: Add doc about hugepages and postcopy > > > > docs/migration.txt | 13 ++++ > > exec.c | 83 +++++++++++++++++++++++ > > include/exec/cpu-common.h | 2 + > > include/exec/memory.h | 1 - > > include/migration/migration.h | 3 + > > include/migration/postcopy-ram.h | 13 ++-- > > linux-headers/linux/userfaultfd.h | 81 +++++++++++++++++++--- > > migration/migration.c | 1 + > > migration/postcopy-ram.c | 138 > > +++++++++++++++++--------------------- > > migration/ram.c | 109 ++++++++++++++++++------------ > > migration/savevm.c | 32 ++++++--- > > migration/trace-events | 2 +- > > 12 files changed, 328 insertions(+), 150 deletions(-) > > > > -- > > 2.9.3 > > > > > -- > Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK >
