From: Radoslaw Zarzynski <rzarzyns@redhat.com>
Date: Wed, 31 Jan 2018 23:51:14 +0000 (+0100)
Subject: osd: avoid the config's get_val() overhead on the read path.
X-Git-Tag: wip-pdonnell-testing-20180317.202121~406^2
X-Git-Url: http://git.apps.os.sepia.ceph.com/?a=commitdiff_plain;h=64c7f313f9bf7a4296b0fbda2e32a1551bb9f5b7;p=ceph-ci.git

osd: avoid the config's get_val() overhead on the read path.

Profiling shows the overhead of the md_config_t::get_val<T>
can be significant. Unfortunately, it is being used in two
critical places across the read path.

The patch resorts to the legacy config infrastructure to
mitigate the performance penalty. It is expected it will
be superseded with a solution that allows to use the new,
intended routines without hurting performance.
`
Signed-off-by: Radoslaw Zarzynski <rzarzyns@redhat.com>
---

diff --git a/src/common/legacy_config_opts.h b/src/common/legacy_config_opts.h
index cf28ca39b3c..b6a53caadbc 100644
--- a/src/common/legacy_config_opts.h
+++ b/src/common/legacy_config_opts.h
@@ -812,6 +812,8 @@ OPTION(osd_fast_info, OPT_BOOL) // use fast info attr, if we can
 // determines whether PGLog::check() compares written out log to stored log
 OPTION(osd_debug_pg_log_writeout, OPT_BOOL)
 OPTION(osd_loop_before_reset_tphandle, OPT_U32) // Max number of loop before we reset thread-pool's handle
+OPTION(osd_max_snap_prune_intervals_per_epoch, OPT_U64) // Max number of snap intervals to report to mgr in pg_stat_t
+
 // default timeout while caling WaitInterval on an empty queue
 OPTION(threadpool_default_timeout, OPT_INT)
 // default wait time for an empty queue before pinging the hb timeout
diff --git a/src/osd/PG.cc b/src/osd/PG.cc
index fd3e268170e..6c580bc8979 100644
--- a/src/osd/PG.cc
+++ b/src/osd/PG.cc
@@ -2912,7 +2912,7 @@ void PG::publish_stats_to_osd()
   if (get_osdmap()->require_osd_release >= CEPH_RELEASE_MIMIC) {
     // share (some of) our purged_snaps via the pg_stats. limit # of intervals
     // because we don't want to make the pg_stat_t structures too expensive.
-    unsigned max = cct->_conf->get_val<uint64_t>("osd_max_snap_prune_intervals_per_epoch");
+    unsigned max = cct->_conf->osd_max_snap_prune_intervals_per_epoch;
     unsigned num = 0;
     auto i = info.purged_snaps.begin();
     while (num < max && i != info.purged_snaps.end()) {
diff --git a/src/osd/PrimaryLogPG.cc b/src/osd/PrimaryLogPG.cc
index c3c62f01aec..85056b44db6 100644
--- a/src/osd/PrimaryLogPG.cc
+++ b/src/osd/PrimaryLogPG.cc
@@ -5494,9 +5494,8 @@ int PrimaryLogPG::do_osd_ops(OpContext *ctx, vector<OSDOp>& ops)
   object_info_t& oi = obs.oi;
   const hobject_t& soid = oi.soid;
   bool skip_data_digest = osd->store->has_builtin_csum() &&
-    g_conf->get_val<bool>("osd_skip_data_digest");
-  auto osd_max_object_size = cct->_conf->get_val<uint64_t>(
-    "osd_max_object_size");
+    cct->_conf->osd_skip_data_digest;
+  const uint64_t osd_max_object_size = cct->_conf->osd_max_object_size;
 
   PGTransaction* t = ctx->op_t.get();