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[174.95.95.253]) by smtp.gmail.com with ESMTPSA id d84sm1833904qke.53.2021.03.05.06.30.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Mar 2021 06:30:36 -0800 (PST) Date: Fri, 5 Mar 2021 09:30:33 -0500 From: Peter Xu To: Kunkun Jiang Subject: Re: [PATCH v3 3/3] migration/ram: Optimize ram_save_host_page() Message-ID: <20210305143033.GF397383@xz-x1> References: <20210305075035.1852-1-jiangkunkun@huawei.com> <20210305075035.1852-4-jiangkunkun@huawei.com> MIME-Version: 1.0 In-Reply-To: <20210305075035.1852-4-jiangkunkun@huawei.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=peterx@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no 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: Juan Quintela , David Edmondson , "Dr . David Alan Gilbert" , "open list:All patches CC here" , =?utf-8?Q?C=C3=A9dric?= Le Goater , Alexey Romko , Zenghui Yu , wanghaibin.wang@huawei.com, Keqian Zhu , Andrey Gruzdev Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, Mar 05, 2021 at 03:50:35PM +0800, Kunkun Jiang wrote: > Starting from pss->page, ram_save_host_page() will check every page > and send the dirty pages up to the end of the current host page or > the boundary of used_length of the block. If the host page size is > a huge page, the step "check" will take a lot of time. > > This will improve performance to use migration_bitmap_find_dirty(). Is there any measurement done? This looks like an optimization, but to me it seems to have changed a lot context that it doesn't need to... Do you think it'll also work to just look up dirty again and update pss->page properly if migration_bitmap_clear_dirty() returned zero? Thanks, > > Signed-off-by: Keqian Zhu > Signed-off-by: Kunkun Jiang > --- > migration/ram.c | 39 +++++++++++++++++++-------------------- > 1 file changed, 19 insertions(+), 20 deletions(-) > > diff --git a/migration/ram.c b/migration/ram.c > index 9fc5b2997c..28215aefe4 100644 > --- a/migration/ram.c > +++ b/migration/ram.c > @@ -1991,6 +1991,8 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss, > int pages = 0; > size_t pagesize_bits = > qemu_ram_pagesize(pss->block) >> TARGET_PAGE_BITS; > + unsigned long hostpage_boundary = > + QEMU_ALIGN_UP(pss->page + 1, pagesize_bits); > unsigned long start_page = pss->page; > int res; > > @@ -2003,30 +2005,27 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss, > int pages_this_iteration = 0; > > /* Check if the page is dirty and send it if it is */ > - if (!migration_bitmap_clear_dirty(rs, pss->block, pss->page)) { > - pss->page++; > - continue; > - } > - > - pages_this_iteration = ram_save_target_page(rs, pss, last_stage); > - if (pages_this_iteration < 0) { > - return pages_this_iteration; > - } > + if (migration_bitmap_clear_dirty(rs, pss->block, pss->page)) { > + pages_this_iteration = ram_save_target_page(rs, pss, last_stage); > + if (pages_this_iteration < 0) { > + return pages_this_iteration; > + } > > - pages += pages_this_iteration; > - pss->page++; > - /* > - * Allow rate limiting to happen in the middle of huge pages if > - * something is sent in the current iteration. > - */ > - if (pagesize_bits > 1 && pages_this_iteration > 0) { > - migration_rate_limit(); > + pages += pages_this_iteration; > + /* > + * Allow rate limiting to happen in the middle of huge pages if > + * something is sent in the current iteration. > + */ > + if (pagesize_bits > 1 && pages_this_iteration > 0) { > + migration_rate_limit(); > + } > } > - } while ((pss->page & (pagesize_bits - 1)) && > + pss->page = migration_bitmap_find_dirty(rs, pss->block, pss->page); > + } while ((pss->page < hostpage_boundary) && > offset_in_ramblock(pss->block, > ((ram_addr_t)pss->page) << TARGET_PAGE_BITS)); > - /* The offset we leave with is the last one we looked at */ > - pss->page--; > + /* The offset we leave with is the min boundary of host page and block */ > + pss->page = MIN(pss->page, hostpage_boundary) - 1; > > res = ram_save_release_protection(rs, pss, start_page); > return (res < 0 ? res : pages); > -- > 2.23.0 > -- Peter Xu