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Tue, 16 Jun 2020 09:35:53 +0000 (UTC) Date: Tue, 16 Jun 2020 10:35:51 +0100 From: "Dr. David Alan Gilbert" To: Keqian Zhu Subject: Re: [PATCH v2] migration: Count new_dirty instead of real_dirty Message-ID: <20200616093551.GA2790@work-vm> References: <20200616021059.25984-1-zhukeqian1@huawei.com> MIME-Version: 1.0 In-Reply-To: <20200616021059.25984-1-zhukeqian1@huawei.com> User-Agent: Mutt/1.14.0 (2020-05-02) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.120; envelope-from=dgilbert@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/16 02:46:07 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action 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: zhang.zhanghailiang@huawei.com, Paolo Bonzini , Juan Quintela , Chao Fan , qemu-devel@nongnu.org, qemu-arm@nongnu.org, jianjay.zhou@huawei.com, wanghaibin.wang@huawei.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Keqian Zhu (zhukeqian1@huawei.com) wrote: > real_dirty_pages becomes equal to total ram size after dirty log sync > in ram_init_bitmaps, the reason is that the bitmap of ramblock is > initialized to be all set, so old path counts them as "real dirty" at > beginning. > > This causes wrong dirty rate and false positive throttling at the end > of first ram save iteration. > > Signed-off-by: Keqian Zhu Since this function already returns num_dirty, why not just change the caller to increment a counter based off the return value? Can you point to the code which is using this value that triggers the throttle? Dave > --- > Changelog: > > v2: > - use new_dirty_pages instead of accu_dirty_pages. > - adjust commit messages. > > --- > include/exec/ram_addr.h | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h > index 7b5c24e928..a95e2e7c25 100644 > --- a/include/exec/ram_addr.h > +++ b/include/exec/ram_addr.h > @@ -443,7 +443,7 @@ 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) > + uint64_t *new_dirty_pages) > { > ram_addr_t addr; > unsigned long word = BIT_WORD((start + rb->offset) >> TARGET_PAGE_BITS); > @@ -469,7 +469,6 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb, > if (src[idx][offset]) { > unsigned long bits = atomic_xchg(&src[idx][offset], 0); > unsigned long new_dirty; > - *real_dirty_pages += ctpopl(bits); > new_dirty = ~dest[k]; > dest[k] |= bits; > new_dirty &= bits; > @@ -502,7 +501,6 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb, > start + addr + offset, > TARGET_PAGE_SIZE, > DIRTY_MEMORY_MIGRATION)) { > - *real_dirty_pages += 1; > long k = (start + addr) >> TARGET_PAGE_BITS; > if (!test_and_set_bit(k, dest)) { > num_dirty++; > @@ -511,6 +509,7 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb, > } > } > > + *new_dirty_pages += num_dirty; > return num_dirty; > } > #endif > -- > 2.19.1 > > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK