From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35434) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VkpSi-0003qF-Bm for qemu-devel@nongnu.org; Mon, 25 Nov 2013 01:16:07 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VkpSa-0003cG-Cs for qemu-devel@nongnu.org; Mon, 25 Nov 2013 01:16:00 -0500 Received: from e31.co.us.ibm.com ([32.97.110.149]:50087) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VkpSa-0003bx-5T for qemu-devel@nongnu.org; Mon, 25 Nov 2013 01:15:52 -0500 Received: from /spool/local by e31.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sun, 24 Nov 2013 23:15:49 -0700 Received: from b03cxnp08026.gho.boulder.ibm.com (b03cxnp08026.gho.boulder.ibm.com [9.17.130.18]) by d03dlp01.boulder.ibm.com (Postfix) with ESMTP id 831421FF001B for ; Sun, 24 Nov 2013 23:15:27 -0700 (MST) Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168]) by b03cxnp08026.gho.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id rAP4Dwg516777350 for ; Mon, 25 Nov 2013 05:13:58 +0100 Received: from d03av02.boulder.ibm.com (localhost [127.0.0.1]) by d03av02.boulder.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id rAP6FkFn021005 for ; Sun, 24 Nov 2013 23:15:46 -0700 Message-ID: <5292EB10.4030705@linux.vnet.ibm.com> Date: Mon, 25 Nov 2013 14:15:44 +0800 From: "Michael R. Hines" MIME-Version: 1.0 References: <1383743088-8139-1-git-send-email-quintela@redhat.com> In-Reply-To: <1383743088-8139-1-git-send-email-quintela@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2 00/39] bitmap handling optimization List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Juan Quintela Cc: chegu_vinod@hp.com, qemu-devel@nongnu.org On 11/06/2013 09:04 PM, Juan Quintela wrote: > Hi > > [v2] > In this version: > - fixed all the comments from last versions (thanks Eric) > - kvm migration bitmap is synchronized using bitmap operations > - qemu bitmap -> migration bitmap is synchronized using bitmap operations > If bitmaps are not properly aligned, we fall back to old code. > Code survives virt-tests, so should be in quite good shape. > > ToDo list: > > - vga ram by default is not aligned in a page number multiple of 64, > > it could be optimized. Kraxel? It syncs the kvm bitmap at least 1 > a second or so? bitmap is only 2048 pages (16MB by default). > We need to change the ram_addr only > > - vga: still more, after we finish migration, vga code continues > synchronizing the kvm bitmap on source machine. Notice that there > is no graphics client connected to the VGA. Worth investigating? > > - I haven't yet meassure speed differences on big hosts. Vinod? > > - Depending of performance, more optimizations to do. > > - debugging printf's still on the code, just to see if we are taking > (or not) the optimized paths. > > And that is all. Please test & comment. > > Thanks, Juan. > > [v1] > This series split the dirty bitmap (8 bits per page, only three used) > into 3 individual bitmaps. Once the conversion is done, operations > are handled by bitmap operations, not bit by bit. > > - *_DIRTY_FLAG flags are gone, now we use memory.h DIRTY_MEMORY_* > everywhere. > > - We set/reset each flag individually > (set_dirty_flags(0xff&~CODE_DIRTY_FLAG)) are gone. > > - Rename several functions to clarify/make consistent things. > > - I know it dont't pass checkpatch for long lines, propper submission > should pass it. We have to have long lines, short variable names, or > ugly line splitting :p > > - DIRTY_MEMORY_NUM: how can one include exec/memory.h into cpu-all.h? > #include it don't work, as a workaround, I have copied its value, but > any better idea? I can always create "exec/migration-flags.h", though. > > - The meat of the code is patch 19. Rest of patches are quite easy > (even that one is not too complex). > > Only optimizations done so far are > set_dirty_range()/clear_dirty_range() that now operates with > bitmap_set/clear. > > Note for Xen: cpu_physical_memory_set_dirty_range() was wrong for xen, > see comment on patch. > > It passes virt-test migration tests, so it should be perfect. > > I post it to ask for comments. > > ToDo list: > > - create a lock for the bitmaps and fold migration bitmap into this > one. This would avoid a copy and make things easier? > > - As this code uses/abuses bitmaps, we need to change the type of the > index from int to long. With an int index, we can only access a > maximum of 8TB guest (yes, this is not urgent, we have a couple of > years to do it). > > - merging KVM <-> QEMU bitmap as a bitmap and not bit-by-bit. > > - spliting the KVM bitmap synchronization into chunks, i.e. not > synchronize all memory, just enough to continue with migration. > > Any further ideas/needs? > > Thanks, Juan. > > PD. Why it took so long? > > Because I was trying to integrate the bitmap on the MemoryRegion > abstraction. Would have make the code cleaner, but hit dead-end > after dead-end. As practical terms, TCG don't know about > MemoryRegions, it has been ported to run on top of them, but > don't use them effective > > > The following changes since commit c2d30667760e3d7b81290d801e567d4f758825ca: > > rtc: remove dead SQW IRQ code (2013-11-05 20:04:03 -0800) > > are available in the git repository at: > > git://github.com/juanquintela/qemu.git bitmap-v2.next > > for you to fetch changes up to d91eff97e6f36612eb22d57c2b6c2623f73d3997: > > migration: synchronize memory bitmap 64bits at a time (2013-11-06 13:54:56 +0100) > > ---------------------------------------------------------------- > Juan Quintela (39): > Move prototypes to memory.h > memory: cpu_physical_memory_set_dirty_flags() result is never used > memory: cpu_physical_memory_set_dirty_range() return void > exec: use accessor function to know if memory is dirty > memory: create function to set a single dirty bit > exec: create function to get a single dirty bit > memory: make cpu_physical_memory_is_dirty return bool > exec: simplify notdirty_mem_write() > memory: all users of cpu_physical_memory_get_dirty used only one flag > memory: set single dirty flags when possible > memory: cpu_physical_memory_set_dirty_range() allways dirty all flags > memory: cpu_physical_memory_mask_dirty_range() always clear a single flag > memory: use DIRTY_MEMORY_* instead of *_DIRTY_FLAG > memory: use bit 2 for migration > memory: make sure that client is always inside range > memory: only resize dirty bitmap when memory size increases > memory: cpu_physical_memory_clear_dirty_flag() result is never used > bitmap: Add bitmap_zero_extend operation > memory: split dirty bitmap into three > memory: unfold cpu_physical_memory_clear_dirty_flag() in its only user > memory: unfold cpu_physical_memory_set_dirty() in its only user > memory: unfold cpu_physical_memory_set_dirty_flag() > memory: make cpu_physical_memory_get_dirty() the main function > memory: cpu_physical_memory_get_dirty() is used as returning a bool > memory: s/mask/clear/ cpu_physical_memory_mask_dirty_range > memory: use find_next_bit() to find dirty bits > memory: cpu_physical_memory_set_dirty_range() now uses bitmap operations > memory: cpu_physical_memory_clear_dirty_range() now uses bitmap operations > memory: s/dirty/clean/ in cpu_physical_memory_is_dirty() > memory: make cpu_physical_memory_reset_dirty() take a length parameter > memory: cpu_physical_memory_set_dirty_tracking() should return void > memory: split cpu_physical_memory_* functions to its own include > memory: unfold memory_region_test_and_clear() > kvm: use directly cpu_physical_memory_* api for tracking dirty pages > kvm: refactor start address calculation > memory: move bitmap synchronization to its own function > memory: syncronize kvm bitmap using bitmaps operations > ram: split function that synchronizes a range > migration: synchronize memory bitmap 64bits at a time > > arch_init.c | 57 ++++++++++++---- > cputlb.c | 10 +-- > exec.c | 75 ++++++++++----------- > include/exec/cpu-all.h | 4 +- > include/exec/cpu-common.h | 4 -- > include/exec/memory-internal.h | 84 ------------------------ > include/exec/memory-physical.h | 143 +++++++++++++++++++++++++++++++++++++++++ > include/exec/memory.h | 10 +-- > include/qemu/bitmap.h | 9 +++ > kvm-all.c | 28 ++------ > memory.c | 17 ++--- > 11 files changed, 260 insertions(+), 181 deletions(-) > create mode 100644 include/exec/memory-physical.h > Well done! The performance gains are very impressive. I also just completed a measurement of this patch for the MC fault tolerance implementation that I posted last month: Here is an example using a 12GB virtual machine (not as big as Vinod's, but not small either), with most of the RAM being aggressively dirtied by a small C program. With MC (micro checkpointing enabled, checkpointing 10 times per second), here is the *per-checkpointing* overheads of the dirty bitmap: 1) BEFORE Juan's Patch: a) Time to retrieve LOGDIRTY from KVM: 33 milliseconds b) Time to synchronize with migration_bitmap from LOGDIRTY bitmap: 86 milliseconds 2) AFTER Juan's Patch: a) Time to retrieve LOGDIRTY from KVM: 17 milliseconds b) Time to synchronize with migration_bitmap from LOGDIRTY bitmap: < 1 millisecond Enormous improvements - very nice. - Michael