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Wed, 8 Jan 2020 13:51:13 +0000 (UTC) Received: from redhat.com (unknown [10.36.118.112]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0758A5C21A; Wed, 8 Jan 2020 13:51:05 +0000 (UTC) From: Juan Quintela To: Auger Eric Subject: Re: [PATCH for-5.0 v11 01/20] migration: Support QLIST migration In-Reply-To: <9ba4d8f1-50b1-4882-77e8-8e7d9a6fac54@redhat.com> (Auger Eric's message of "Wed, 8 Jan 2020 14:40:47 +0100") 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> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) Date: Wed, 08 Jan 2020 14:51:01 +0100 Message-ID: <8736cqgipm.fsf@secure.laptop> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-MC-Unique: ec9nmA8-NWyfNl1oiY-xmg-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 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: , Reply-To: quintela@redhat.com Cc: yang.zhong@intel.com, peter.maydell@linaro.org, kevin.tian@intel.com, tnowicki@marvell.com, mst@redhat.com, jean-philippe.brucker@arm.com, armbru@redhat.com, "Dr. David Alan Gilbert" , peterx@redhat.com, qemu-devel@nongnu.org, 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" 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 =3D g_malloc(size); >>>> + ret =3D 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. >>=20 >> This was my fault (integrated as this is). >>=20 >> 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 =3D NULL; while (qemu_get_byte(f)) { elm =3D g_malloc(size); ret =3D 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 =3D 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. But as said, we can move that to another patch. Later, Juan.