From dad45ab2be9d5ce033ddba328204b06f2d10f0ed Mon Sep 17 00:00:00 2001 From: Wei Yang Date: Tue, 6 Aug 2019 08:46:47 +0800 Subject: [PATCH] migration/postcopy: simplify calculation of run_start and fixup_start_addr The purpose of the calculation is to find a HostPage which is partially dirty. * fixup_start_addr points to the start of the HostPage to discard * run_start points to the next HostPage to check While in the middle stage, there would two cases for run_start: * aligned with HostPage means this is not partially dirty * not aligned means this is partially dirty When it is aligned, no work and calculation is necessary. run_start already points to the start of next HostPage and is ready to continue. When it is not aligned, the calculation could be simplified with: * fixup_start_addr = QEMU_ALIGN_DOWN(run_start, host_ratio) * run_start = QEMU_ALIGN_UP(run_start, host_ratio) By doing so, run_start always points to the next HostPage to check. fixup_start_addr always points to the HostPage to discard. Signed-off-by: Wei Yang Message-Id: <20190806004648.8659-2-richardw.yang@linux.intel.com> Reviewed-by: Dr. David Alan Gilbert Signed-off-by: Dr. David Alan Gilbert --- migration/ram.c | 34 +++++++--------------------------- 1 file changed, 7 insertions(+), 27 deletions(-) diff --git a/migration/ram.c b/migration/ram.c index f428639af5..d2184c3cfc 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -2955,7 +2955,6 @@ static void postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass, } while (run_start < pages) { - unsigned long fixup_start_addr; unsigned long host_offset; /* @@ -2963,45 +2962,26 @@ static void postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass, * page, then we need to fixup this host page. */ host_offset = run_start % host_ratio; - if (host_offset) { - fixup_start_addr = run_start - host_offset; - /* - * This host page has gone, the next loop iteration starts - * from after the fixup - */ - run_start = fixup_start_addr + host_ratio; - } else { + if (!host_offset) { /* Find the end of this run */ - unsigned long run_end; if (unsent_pass) { - run_end = find_next_bit(unsentmap, pages, run_start + 1); + run_start = find_next_bit(unsentmap, pages, run_start + 1); } else { - run_end = find_next_zero_bit(bitmap, pages, run_start + 1); + run_start = find_next_zero_bit(bitmap, pages, run_start + 1); } /* * If the end isn't at the start of a host page, then the * run doesn't finish at the end of a host page * and we need to discard. */ - host_offset = run_end % host_ratio; - if (host_offset) { - fixup_start_addr = run_end - host_offset; - /* - * This host page has gone, the next loop iteration starts - * from after the fixup - */ - run_start = fixup_start_addr + host_ratio; - } else { - /* - * No discards on this iteration, next loop starts from - * next sent/dirty page - */ - run_start = run_end + 1; - } + host_offset = run_start % host_ratio; } if (host_offset) { unsigned long page; + unsigned long fixup_start_addr = QEMU_ALIGN_DOWN(run_start, + host_ratio); + run_start = QEMU_ALIGN_UP(run_start, host_ratio); /* Tell the destination to discard this page */ if (unsent_pass || !test_bit(fixup_start_addr, unsentmap)) { -- 2.11.4.GIT