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Re: [Qemu-devel] Ping: [PATCH] qobject: object_property_add() performanc
From: |
Peter Crosthwaite |
Subject: |
Re: [Qemu-devel] Ping: [PATCH] qobject: object_property_add() performance improvement |
Date: |
Thu, 4 Jun 2015 01:07:19 -0700 |
On Thu, Jun 4, 2015 at 12:35 AM, Pavel Fedin <address@hidden> wrote:
> Hello Luiz! Have you missed this ?
>
> Kind regards,
> Pavel Fedin
> Expert Engineer
> Samsung Electronics Research center Russia
>
>
>> -----Original Message-----
>> From: address@hidden [mailto:qemu-devel-
>> address@hidden On Behalf Of Pavel Fedin
>> Sent: Thursday, May 28, 2015 11:42 AM
>> To: address@hidden
>> Cc: 'Luiz Capitulino'
>> Subject: [Qemu-devel] [PATCH] qobject: object_property_add() performance
>> improvement
>>
>> The function originally behaves very badly when adding properties with
>> "[*]" suffix.
>> Nomnally these are used for numbering IRQ pins. In order to find the correct
>> starting
"normally"
>> number the function started from zero and checked for duplicates. This took
>> incredibly
>> long time with large number of CPUs because number of IRQ pins on some
>> architectures
> (like
>> ARM GICv3) gets multiplied by number of CPUs.
>> The solution is to add one more property which caches last used index so
>> that
> duplication
>> check is not repeated thousands of times. Every time an array is expanded
>> the index is
>> picked up from this cache. Cache property is a uint32_t and has the original
>> name of the
>> array ('name[*]') for simplicity.
>> Some more improvements:
>> - Call object_property_add_single() instead of recursing into itself - keeps
>> off
> memcmp()
>> check every time when its result is already known.
>> - Allocate name_no_array only once and not every time for every property
>> (there can be
>> thousands of them)
>> The modification decreases qemu startup time with 32 ARMv8 CPUs by a factor
>> of 2 (~10
> sec
>> vs ~20 sec).
>>
>> Signed-off-by: Pavel Fedin <address@hidden>
>> ---
>> qom/object.c | 89
>> ++++++++++++++++++++++++++++++++++++++++++------------------
>> 1 file changed, 62 insertions(+), 27 deletions(-)
>>
>> diff --git a/qom/object.c b/qom/object.c
>> index b8dff43..72480bc 100644
>> --- a/qom/object.c
>> +++ b/qom/object.c
>> @@ -10,6 +10,8 @@
>> * See the COPYING file in the top-level directory.
>> */
>>
>> +#include <glib/gprintf.h>
>> +
>> #include "qom/object.h"
>> #include "qemu-common.h"
>> #include "qapi/visitor.h"
>> @@ -721,35 +723,14 @@ void object_unref(Object *obj)
>> }
>> }
>>
>> -ObjectProperty *
>> -object_property_add(Object *obj, const char *name, const char *type,
>> - ObjectPropertyAccessor *get,
>> - ObjectPropertyAccessor *set,
>> - ObjectPropertyRelease *release,
>> - void *opaque, Error **errp)
>> +static ObjectProperty *
>> +object_property_add_single(Object *obj, const char *name, const char *type,
>> + ObjectPropertyAccessor *get,
>> + ObjectPropertyAccessor *set,
>> + ObjectPropertyRelease *release,
>> + void *opaque, Error **errp)
>> {
>> ObjectProperty *prop;
>> - size_t name_len = strlen(name);
>> -
>> - if (name_len >= 3 && !memcmp(name + name_len - 3, "[*]", 4)) {
>> - int i;
>> - ObjectProperty *ret;
>> - char *name_no_array = g_strdup(name);
>> -
>> - name_no_array[name_len - 3] = '\0';
>> - for (i = 0; ; ++i) {
>> - char *full_name = g_strdup_printf("%s[%d]", name_no_array, i);
>> -
>> - ret = object_property_add(obj, full_name, type, get, set,
>> - release, opaque, NULL);
>> - g_free(full_name);
>> - if (ret) {
>> - break;
>> - }
>> - }
>> - g_free(name_no_array);
>> - return ret;
>> - }
>>
>> QTAILQ_FOREACH(prop, &obj->properties, node) {
>> if (strcmp(prop->name, name) == 0) {
>> @@ -774,6 +755,60 @@ object_property_add(Object *obj, const char *name,
>> const char
> *type,
>> return prop;
>> }
>>
>> +static void property_get_uint32_ptr(Object *obj, Visitor *v,
>> + void *opaque, const char *name,
>> + Error **errp);
>> +
>> +ObjectProperty *
>> +object_property_add(Object *obj, const char *name, const char *type,
>> + ObjectPropertyAccessor *get,
>> + ObjectPropertyAccessor *set,
>> + ObjectPropertyRelease *release,
>> + void *opaque, Error **errp)
>> +{
>> + size_t name_len = strlen(name);
>> +
>> + if (name_len >= 3 && !memcmp(name + name_len - 3, "[*]", 4)) {
Rather than if this large block, negate the condition and use
object_property_add_single to short return.
>> + int i;
>> + ObjectProperty *ret, *count;
>> + /* 10 characters for maximum possible integer number */
>> + char *name_no_array = g_malloc(name_len + 10);
>> +
>> + count = object_property_find(obj, name, NULL);
>> + if (count == NULL) {
Indentation doesn't look right.
>> + void *v = g_malloc0(sizeof(uint32_t));
>> +
Can you allocate name_no_array here along with the count in a small
struct to save on some allocs and memcpys?
>> + /* This is the same as object_property_add_uint32_ptr(), but:
>> + * - Slightly faster and returns pointer
>> + * - Will not recurse here so that we can use
>> + * raw name with [*] here */
newline before */
>> + count = object_property_add_single(obj, name, "uint32",
>> + property_get_uint32_ptr,
>> NULL,
Do you need to register the getter or can you make it completely
opaque instead? Alternatively can you register the setter and use
set/get instead of going hands on with the property opaque pointer?
>> + NULL, v, &error_abort);
>> + }
>> +
>> + name_len -= 2;
>> + memcpy(name_no_array, name, name_len);
Can you drop the "[" as well? You will have one less byte to memcpy
and pick it up again in the sprintf so I dont see a huge perf
advantage. Makes the code below more readable.
>> +
>> + for (i = *((uint32_t *)count->opaque); ; ++i) {
Parentheses not needed.
>> + g_sprintf(&name_no_array[name_len], "%d]", i);
>> +
Indentation.
Regards,
Peter
>> + ret = object_property_add_single(obj, name_no_array, type, get,
>> set,
>> + release, opaque, NULL);
>> + if (ret) {
>> + break;
>> + }
>> + }
>> + *((uint32_t *)count->opaque) = i + 1;
>> +
>> + g_free(name_no_array);
>> + return ret;
>> + }
>> +
>> + return object_property_add_single(obj, name, type,
>> + get, set, release, opaque, errp);
>> +}
>> +
>> ObjectProperty *object_property_find(Object *obj, const char *name,
>> Error **errp)
>> {
>> --
>> 1.9.5.msysgit.0
>>
>
>
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