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[2001:8b0:bb71:7140:64::dea8]) by smtp.gmail.com with ESMTPSA id n18sm4752401wrp.58.2020.08.26.03.53.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Aug 2020 03:53:08 -0700 (PDT) Received: from localhost (disaster-area.hh.sledj.net [local]) by disaster-area.hh.sledj.net (OpenSMTPD) with ESMTPA id 1d2838e8; Wed, 26 Aug 2020 10:53:07 +0000 (UTC) To: "Dr. David Alan Gilbert" Subject: Re: [PATCH v5 03/12] migration/dirtyrate: Add RamlockDirtyInfo to store sampled page info In-Reply-To: <20200826103330.GB2726@work-vm> References: <1598260480-64862-1-git-send-email-zhengchuan@huawei.com> <1598260480-64862-4-git-send-email-zhengchuan@huawei.com> <20200826103330.GB2726@work-vm> X-HGTTG: heart-of-gold From: David Edmondson Date: Wed, 26 Aug 2020 11:53:07 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Received-SPF: neutral client-ip=2a00:1450:4864:20::441; envelope-from=dme@dme.org; helo=mail-wr1-x441.google.com X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. That's all we know. X-Spam_score_int: -10 X-Spam_score: -1.1 X-Spam_bar: - X-Spam_report: (-1.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_NEUTRAL=0.779, UNPARSEABLE_RELAY=0.001 autolearn=no 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: alex.chen@huawei.com, berrange@redhat.com, zhang.zhanghailiang@huawei.com, quintela@redhat.com, qemu-devel@nongnu.org, xiexiangyou@huawei.com, Chuan Zheng , ann.zhuangyanying@huawei.com, fangying1@huawei.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wednesday, 2020-08-26 at 11:33:30 +01, Dr. David Alan Gilbert wrote: > * David Edmondson (dme@dme.org) wrote: >> On Monday, 2020-08-24 at 17:14:31 +08, Chuan Zheng wrote: >> >> > Add RamlockDirtyInfo to store sampled page info of each ramblock. >> > >> > Signed-off-by: Chuan Zheng >> > --- >> > migration/dirtyrate.h | 18 ++++++++++++++++++ >> > 1 file changed, 18 insertions(+) >> > >> > diff --git a/migration/dirtyrate.h b/migration/dirtyrate.h >> > index 33669b7..70000da 100644 >> > --- a/migration/dirtyrate.h >> > +++ b/migration/dirtyrate.h >> > @@ -19,6 +19,11 @@ >> > */ >> > #define DIRTYRATE_DEFAULT_SAMPLE_PAGES 512 >> > >> > +/* >> > + * Record ramblock idstr >> > + */ >> > +#define RAMBLOCK_INFO_MAX_LEN 256 >> > + >> > /* Take 1s as default for calculation duration */ >> > #define DEFAULT_FETCH_DIRTYRATE_TIME_SEC 1 >> > >> > @@ -27,6 +32,19 @@ struct DirtyRateConfig { >> > int64_t sample_period_seconds; /* time duration between two sampling */ >> > }; >> > >> > +/* >> > + * Store dirtypage info for each ramblock. >> > + */ >> > +struct RamblockDirtyInfo { >> > + char idstr[RAMBLOCK_INFO_MAX_LEN]; /* idstr for each ramblock */ >> > + uint8_t *ramblock_addr; /* base address of ramblock we measure */ >> > + uint64_t ramblock_pages; /* ramblock size in 4K-page */ >> >> It's probably a stupid question, but why not store a pointer to the >> RAMBlock rather than copying some of the details? > > I think I figured that out in the last round; this code runs as: > > rcu lock { > calculate initial CRCs > } > > > rcu lock { > calculate new CRCs > } > > A RAMBlock might get deleted between the two. Makes sense, thanks. dme. -- Why does it have to be like this? I can never tell.