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Wed, 8 Jan 2020 14:02:49 +0000 (UTC) Subject: Re: [PATCH for-5.0 v11 01/20] migration: Support QLIST migration To: quintela@redhat.com References: <20191122182943.4656-1-eric.auger@redhat.com> <20191122182943.4656-2-eric.auger@redhat.com> <20191127114621.GG3016@work-vm> <87muaygk5l.fsf@secure.laptop> <9ba4d8f1-50b1-4882-77e8-8e7d9a6fac54@redhat.com> <8736cqgipm.fsf@secure.laptop> From: Auger Eric Message-ID: Date: Wed, 8 Jan 2020 15:02:48 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <8736cqgipm.fsf@secure.laptop> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-MC-Unique: 0JHdwa2CM1OTDf0I1Gxqpw-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 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: yang.zhong@intel.com, peter.maydell@linaro.org, kevin.tian@intel.com, qemu-devel@nongnu.org, tnowicki@marvell.com, mst@redhat.com, jean-philippe.brucker@arm.com, armbru@redhat.com, peterx@redhat.com, "Dr. David Alan Gilbert" , bharatb.linux@gmail.com, qemu-arm@nongnu.org, eric.auger.pro@gmail.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Juan, On 1/8/20 2:51 PM, Juan Quintela wrote: > Auger Eric wrote: >> Hi Juan, >> >> On 1/8/20 2:19 PM, Juan Quintela wrote: >>> "Dr. David Alan Gilbert" wrote: >>>> * Eric Auger (eric.auger@redhat.com) wrote: >>>>> Support QLIST migration using the same principle as QTAILQ: >>>>> 94869d5c52 ("migration: migrate QTAILQ"). >>>>> >>>>> The VMSTATE_QLIST_V macro has the same proto as VMSTATE_QTAILQ_V. >>>>> The change mainly resides in QLIST RAW macros: QLIST_RAW_INSERT_HEAD >>>>> and QLIST_RAW_REVERSE. >>>>> >>>>> Tests also are provided. >>>>> >>>>> Signed-off-by: Eric Auger >>>>> >>>>> + while (qemu_get_byte(f)) { >>>>> + elm = g_malloc(size); >>>>> + ret = vmstate_load_state(f, vmsd, elm, version_id); >>>>> + if (ret) { >>>>> + error_report("%s: failed to load %s (%d)", field->name, >>>>> + vmsd->name, ret); >>>>> + g_free(elm); >>>>> + return ret; >>>>> + } >>>>> + QLIST_RAW_INSERT_HEAD(pv, elm, entry_offset); >>>>> + } >>>>> + QLIST_RAW_REVERSE(pv, elm, entry_offset); >>>> >>>> Can you explain why you need to do a REVERSE on the loaded list, >>>> rather than using doing a QLIST_INSERT_AFTER to always insert at >>>> the end? >>>> >>>> Other than that it looks good. >>> >>> This was my fault (integrated as this is). >>> >>> Old code had a "walk to the end of the list" and then insert. >>> I told it was way faster just to insert and the beggining and then >>> reverse. I didn't noticed that we had the previous element to know >>> where to insert. >> >> Not sure I get your comment. To insert at the end one needs to walk >> though the list. The head has no prev pointer pointing to the tail as >> opposed to the queue. So I understood Dave's comment as "just explain >> why you prefered this solution against the QLIST_INSERT_AFTER alternative. > > You have the previous inserted element, so it is kind of easy O:-) > > prev = NULL; > while (qemu_get_byte(f)) { > elm = g_malloc(size); > ret = vmstate_load_state(f, vmsd, elm, version_id); > if (ret) { > error_report("%s: failed to load %s (%d)", field->name, > vmsd->name, ret); > g_free(elm); > return ret; > } > if (!prev) { > QLIST_RAW_INSERT_HEAD(pv, elm, entry_offset); > } else { > QLIST_RAW_INSERT_AFTER(prev, elm, entry_offset); > } > prev = elm; > } > > And yes, I realize that there is no QLIST_RAW_INSTERT_AFTER() (it is > QLIST_INSERT_AFTER). And no, I haven't took the time to understand the > different between QLIST and QLIST_RAW. From a quick look, it seems that > QLIST_RAW is embededed inside other structure. Ah OK I get it now. Yes indeed that looks simpler. > > But as said, we can move that to another patch. OK. Thanks Eric > > Later, Juan. > >