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Re: [PATCH for-5.1 5/5] qom: Make info qom-tree sort children more effic
From: |
Markus Armbruster |
Subject: |
Re: [PATCH for-5.1 5/5] qom: Make info qom-tree sort children more efficiently |
Date: |
Tue, 21 Jul 2020 17:39:20 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) |
"Dr. David Alan Gilbert" <dgilbert@redhat.com> 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 <armbru@redhat.com>
>> ---
>> 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 <dgilbert@redhat.com>
>
> 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!
- [PATCH for-5.1 0/5] qom: HMP command fixes, Markus Armbruster, 2020/07/14
- [PATCH for-5.1 4/5] qom: Document object_get_canonical_path() returns malloced string, Markus Armbruster, 2020/07/14
- [PATCH for-5.1 5/5] qom: Make info qom-tree sort children more efficiently, Markus Armbruster, 2020/07/14
- [PATCH for-5.1 2/5] qom: Plug memory leak in "info qom-tree", Markus Armbruster, 2020/07/14
- [PATCH for-5.1 1/5] qdev: Fix device_add DRIVER, help to print to monitor, Markus Armbruster, 2020/07/14
- [PATCH for-5.1 3/5] qom: Change object_get_canonical_path_component() not to malloc, Markus Armbruster, 2020/07/14