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conf: Optimize the iothreadid initialization

Browse Source 
https://bugzilla.redhat.com/show_bug.cgi?id=1264008

The existing algorithm assumed that someone was making small, incremental
changes; however, it is possible to change iothreads from 0 (or relatively
small number) to some really large number and the algorithm would possibly
spin its wheels doing unnecessary searches.

So, optimize the algorithm using a bitmap to find available iothread_id's
starting at 1 that aren't already defined by a "<thread id='#'>" and
filling in the iothreadids array with those iothread_id values.
This commit is contained in:
John Ferlan 2015-10-13 08:26:27 -04:00
parent cc2d49f9be
commit bb02d4c429
1 changed files with 32 additions and 8 deletions
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40
src/conf/domain_conf.c
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@ -2332,8 +2332,11 @@ virDomainIOThreadIDDefArrayFree(virDomainIOThreadIDDefPtr *def,
static int
virDomainIOThreadIDDefArrayInit(virDomainDefPtr def)
{
unsigned int iothread_id = 1;
int retval = -1;
size_t i;
ssize_t nxt = -1;
virDomainIOThreadIDDefPtr iothrid = NULL;
virBitmapPtr thrmap = NULL;
/* Same value (either 0 or some number), then we have none to fill in or
* the iothreadid array was filled from the XML
@ -2341,19 +2344,40 @@ virDomainIOThreadIDDefArrayInit(virDomainDefPtr def)
if (def->iothreads == def->niothreadids)
return 0;
while (def->niothreadids != def->iothreads) {
if (!virDomainIOThreadIDFind(def, iothread_id)) {
virDomainIOThreadIDDefPtr iothrid;
if (!(iothrid = virDomainIOThreadIDAdd(def, iothread_id)))
/* iothread's are numbered starting at 1, account for that */
if (!(thrmap = virBitmapNew(def->iothreads + 1)))
goto error;
virBitmapSetAll(thrmap);
/* Clear 0 since we don't use it, then mark those which are
* already provided by the user */
ignore_value(virBitmapClearBit(thrmap, 0));
for (i = 0; i < def->niothreadids; i++)
ignore_value(virBitmapClearBit(thrmap,
def->iothreadids[i]->iothread_id));
/* resize array */
if (VIR_REALLOC_N(def->iothreadids, def->iothreads) < 0)
goto error;
/* Populate iothreadids[] using the set bit number from thrmap */
while (def->niothreadids < def->iothreads) {
if ((nxt = virBitmapNextSetBit(thrmap, nxt)) < 0) {
virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
_("failed to populate iothreadids"));
goto error;
}
if (VIR_ALLOC(iothrid) < 0)
goto error;
iothrid->iothread_id = nxt;
iothrid->autofill = true;
def->iothreadids[def->niothreadids++] = iothrid;
}
iothread_id++;
}
retval = 0;
error:
virBitmapFree(thrmap);
return retval;
}