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Optimize: Keep cont->mutex locked, during probe the bucket by hash object within HostDBProcessor::getby #4916

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Merged
oknet merged 1 commit into from
Feb 11, 2019
Merged

Optimize: Keep cont->mutex locked, during probe the bucket by hash object within HostDBProcessor::getby #4916

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17 changes: 8 additions & 9 deletions iocore/hostdb/HostDB.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -634,19 +634,18 @@ HostDBProcessor::getby(Continuation *cont, const char *hostname, int len, sockad
// Attempt to find the result in-line, for level 1 hits
//
if (!aforce_dns) {
bool loop;
do {
MUTEX_TRY_LOCK(lock, cont->mutex, thread);
bool loop = lock.is_locked();
while (loop) {
loop = false; // Only loop on explicit set for retry.
// find the partition lock
//
// TODO: Could we reuse the "mutex" above safely? I think so but not sure.
Ptr<ProxyMutex> bmutex = hostDB.refcountcache->lock_for_key(hash.hash.fold());
MUTEX_TRY_LOCK(lock, bmutex, thread);
MUTEX_TRY_LOCK(lock2, cont->mutex, thread);
Ptr<ProxyMutex> bucket_mutex = hostDB.refcountcache->lock_for_key(hash.hash.fold());
MUTEX_TRY_LOCK(lock2, bucket_mutex, thread);

if (lock.is_locked() && lock2.is_locked()) {
if (lock2.is_locked()) {
// If we can get the lock and a level 1 probe succeeds, return
Ptr<HostDBInfo> r = probe(bmutex, hash, aforce_dns);
Ptr<HostDBInfo> r = probe(bucket_mutex, hash, aforce_dns);
if (r) {
if (r->is_failed() && hostname) {
loop = check_for_retry(hash.db_mark, host_res_style);
Expand All @@ -662,7 +661,7 @@ HostDBProcessor::getby(Continuation *cont, const char *hostname, int len, sockad
hash.refresh(); // only on reloop, because we've changed the family.
}
}
} while (loop);
}
}
Debug("hostdb", "delaying force %d answer for %s", aforce_dns,
hostname ? hostname : ats_is_ip(ip) ? ats_ip_ntop(ip, ipb, sizeof ipb) : "<null>");
Expand Down