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Tue, 21 Jul 2020 15:39:22 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id A6669111CA27; Tue, 21 Jul 2020 17:39:20 +0200 (CEST) From: Markus Armbruster To: "Dr. David Alan Gilbert" Subject: Re: [PATCH for-5.1 5/5] qom: Make info qom-tree sort children more efficiently References: <20200714160202.3121879-1-armbru@redhat.com> <20200714160202.3121879-6-armbru@redhat.com> <20200721153214.GB27840@work-vm> Date: Tue, 21 Jul 2020 17:39:20 +0200 In-Reply-To: <20200721153214.GB27840@work-vm> (David Alan Gilbert's message of "Tue, 21 Jul 2020 16:32:14 +0100") Message-ID: <87k0yw513r.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=205.139.110.120; envelope-from=armbru@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/21 10:58:38 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 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_H2=-1, 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: lvivier@redhat.com, thuth@redhat.com, berrange@redhat.com, ehabkost@redhat.com, qemu-devel@nongnu.org, Markus Armbruster , pbonzini@redhat.com, alex.bennee@linaro.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" "Dr. David Alan Gilbert" writes: > * Markus Armbruster (armbru@redhat.com) wrote: >> Commit e8c9e65816 "qom: Make "info qom-tree" show children sorted" >> sorts children the simple, stupid, quadratic way. I thought the >> number of children would be small enough for this not to matter. I >> was wrong: there are outliers with several hundred children, e.g ARM >> machines nuri and smdkc210 each have a node with 513 children. > > Big Power systems can have thousands. > >> While n^2 sorting isn't noticeable in normal, human usage even for >> n=513, it can be quite noticeable in certain automated tests. In >> particular, the sort made device-introspect-test even slower. Commit >> 3e7b80f84d "tests: improve performance of device-introspect-test" just >> fixed that by cutting back its excessive use of "info qom-tree". >> Sorting more efficiently makes sense regardless, so do it. >> >> Signed-off-by: Markus Armbruster >> --- >> qom/qom-hmp-cmds.c | 25 +++++++++++++------------ >> 1 file changed, 13 insertions(+), 12 deletions(-) >> >> diff --git a/qom/qom-hmp-cmds.c b/qom/qom-hmp-cmds.c >> index 4032c96089..8861a109d5 100644 >> --- a/qom/qom-hmp-cmds.c >> +++ b/qom/qom-hmp-cmds.c >> @@ -94,25 +94,23 @@ typedef struct QOMCompositionState { >> >> static void print_qom_composition(Monitor *mon, Object *obj, int indent); >> >> -static int qom_composition_compare(const void *a, const void *b, void *ignore) >> +static int qom_composition_compare(const void *a, const void *b) >> { >> - return g_strcmp0(object_get_canonical_path_component(a), >> - object_get_canonical_path_component(b)); >> + return g_strcmp0(object_get_canonical_path_component(*(Object **)a), >> + object_get_canonical_path_component(*(Object **)b)); >> } >> >> static int insert_qom_composition_child(Object *obj, void *opaque) >> { >> - GQueue *children = opaque; >> - >> - g_queue_insert_sorted(children, obj, qom_composition_compare, NULL); >> + g_array_append_val(opaque, obj); >> return 0; >> } >> >> static void print_qom_composition(Monitor *mon, Object *obj, int indent) >> { >> + GArray *children = g_array_new(false, false, sizeof(Object *)); >> const char *name; >> - GQueue children; >> - Object *child; >> + int i; >> >> if (obj == object_get_root()) { >> name = ""; >> @@ -122,11 +120,14 @@ static void print_qom_composition(Monitor *mon, Object *obj, int indent) >> monitor_printf(mon, "%*s/%s (%s)\n", indent, "", name, >> object_get_typename(obj)); >> >> - g_queue_init(&children); >> - object_child_foreach(obj, insert_qom_composition_child, &children); >> - while ((child = g_queue_pop_head(&children))) { >> - print_qom_composition(mon, child, indent + 2); >> + object_child_foreach(obj, insert_qom_composition_child, children); >> + g_array_sort(children, qom_composition_compare); >> + >> + for (i = 0; i < children->len; i++) { >> + print_qom_composition(mon, g_array_index(children, Object *, i), >> + indent + 2); >> } >> + g_array_free(children, TRUE); > > So I think that's OK, so : > > Reviewed-by: Dr. David Alan Gilbert > > Can you just convince me that 'TRUE' in the array_free? g_array_free(children, TRUE) frees both children and children->data. It returns null. This is what we want here. g_array_free(children, FALSE) frees only children, and returns children->data. Occasionally useful. https://developer.gnome.org/glib/2.62/glib-Arrays.html#g-array-free I definitely would have made this two separate functions. Thanks!