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([2001:b07:6468:f312:e427:3beb:1110:dda2]) by smtp.gmail.com with ESMTPSA id k124sm36507584wmk.47.2019.07.17.02.16.20 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Wed, 17 Jul 2019 02:16:20 -0700 (PDT) To: Wei Yang , "Dr. David Alan Gilbert" References: <20190430034412.12935-1-richardw.yang@linux.intel.com> <20190430034412.12935-3-richardw.yang@linux.intel.com> <20190514142108.GG2753@work-vm> <20190717011337.GA14233@richard> From: Paolo Bonzini Openpgp: preference=signencrypt Message-ID: <4b3016cd-de7b-3ab7-76b8-8608cb1239b6@redhat.com> Date: Wed, 17 Jul 2019 11:16:19 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20190717011337.GA14233@richard> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.85.221.67 Subject: Re: [Qemu-devel] [PATCH 2/3] migration/ram.c: start of cpu_physical_memory_sync_dirty_bitmap is always 0 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org, quintela@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 17/07/19 03:13, Wei Yang wrote: > On Tue, May 14, 2019 at 03:21:08PM +0100, Dr. David Alan Gilbert wrote: >> * Wei Yang (richardw.yang@linux.intel.com) wrote: >>> Since start of cpu_physical_memory_sync_dirty_bitmap is always 0, we can >>> remove this parameter and simplify the calculation a bit. >>> >>> Signed-off-by: Wei Yang >> >> So I think you're right it's currently unused; however, lets ask >> Paolo: Do we need to keep this parameter for flexiblity? >> > > Hey, Paolo > > Do you have some spare time to give some insight? I think it's cleaner to leave the start argument in place. However, I'll note that in migration_bitmap_sync_range the length argument is always block->used_length so that's also unnecessary (you already have block). Paolo >> Dave >> >>> --- >>> include/exec/ram_addr.h | 15 ++++++--------- >>> migration/ram.c | 2 +- >>> 2 files changed, 7 insertions(+), 10 deletions(-) >>> >>> diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h >>> index 9ecd911c3e..3dfb2d52fb 100644 >>> --- a/include/exec/ram_addr.h >>> +++ b/include/exec/ram_addr.h >>> @@ -409,18 +409,16 @@ static inline void cpu_physical_memory_clear_dirty_range(ram_addr_t start, >>> >>> static inline >>> uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb, >>> - ram_addr_t start, >>> ram_addr_t length, >>> uint64_t *real_dirty_pages) >>> { >>> ram_addr_t addr; >>> - unsigned long word = BIT_WORD((start + rb->offset) >> TARGET_PAGE_BITS); >>> + unsigned long word = BIT_WORD(rb->offset >> TARGET_PAGE_BITS); >>> uint64_t num_dirty = 0; >>> unsigned long *dest = rb->bmap; >>> >>> - /* start address and length is aligned at the start of a word? */ >>> - if (((word * BITS_PER_LONG) << TARGET_PAGE_BITS) == >>> - (start + rb->offset) && >>> + /* offset and length is aligned at the start of a word? */ >>> + if (((word * BITS_PER_LONG) << TARGET_PAGE_BITS) == (rb->offset) && >>> !(length & ((BITS_PER_LONG << TARGET_PAGE_BITS) - 1))) { >>> int k; >>> int nr = BITS_TO_LONGS(length >> TARGET_PAGE_BITS); >>> @@ -428,14 +426,13 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb, >>> unsigned long idx = (word * BITS_PER_LONG) / DIRTY_MEMORY_BLOCK_SIZE; >>> unsigned long offset = BIT_WORD((word * BITS_PER_LONG) % >>> DIRTY_MEMORY_BLOCK_SIZE); >>> - unsigned long page = BIT_WORD(start >> TARGET_PAGE_BITS); >>> >>> rcu_read_lock(); >>> >>> src = atomic_rcu_read( >>> &ram_list.dirty_memory[DIRTY_MEMORY_MIGRATION])->blocks; >>> >>> - for (k = page; k < page + nr; k++) { >>> + for (k = 0; k < nr; k++) { >>> if (src[idx][offset]) { >>> unsigned long bits = atomic_xchg(&src[idx][offset], 0); >>> unsigned long new_dirty; >>> @@ -458,11 +455,11 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb, >>> >>> for (addr = 0; addr < length; addr += TARGET_PAGE_SIZE) { >>> if (cpu_physical_memory_test_and_clear_dirty( >>> - start + addr + offset, >>> + addr + offset, >>> TARGET_PAGE_SIZE, >>> DIRTY_MEMORY_MIGRATION)) { >>> *real_dirty_pages += 1; >>> - long k = (start + addr) >> TARGET_PAGE_BITS; >>> + long k = addr >> TARGET_PAGE_BITS; >>> if (!test_and_set_bit(k, dest)) { >>> num_dirty++; >>> } >>> diff --git a/migration/ram.c b/migration/ram.c >>> index 9948b2d021..1def8122e9 100644 >>> --- a/migration/ram.c >>> +++ b/migration/ram.c >>> @@ -1646,7 +1646,7 @@ static void migration_bitmap_sync_range(RAMState *rs, RAMBlock *rb, >>> ram_addr_t length) >>> { >>> rs->migration_dirty_pages += >>> - cpu_physical_memory_sync_dirty_bitmap(rb, 0, length, >>> + cpu_physical_memory_sync_dirty_bitmap(rb, length, >>> &rs->num_dirty_pages_period); >>> } >>> >>> -- >>> 2.19.1 >>> >> -- >> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK >