Fix WRITE_STALL start_time (#12147)

akankshamahajan15 · facebook-github-bot · commit cd577f605948 · 2023-12-14T13:45:06.000-08:00
Summary: `Delayed` is set true in two cases. One is when `delay` is specified. Other one is in the `while` loop - https://github.com/facebook/rocksdb/blob/cd21e4e69d76ec4ec3b080c8cdae016ac2309cc5/db/db_impl/db_impl_write.cc#L1876 However start_time is not initialized in second case, resulting in time_delayed = immutable_db_options_.clock->NowMicros() - 0(start_time); Pull Request resolved: #12147 Test Plan: Existing CircleCI Reviewed By: cbi42 Differential Revision: D52173481 Pulled By: akankshamahajan15 fbshipit-source-id: fb9183b24c191d287a1d715346467bee66190f98
diff --git a/db/db_impl/db_impl_write.cc b/db/db_impl/db_impl_write.cc
@@ -1839,11 +1839,12 @@ Status DBImpl::DelayWrite(uint64_t num_bytes, WriteThread& write_thread,
       delay = 0;
     }
     TEST_SYNC_POINT("DBImpl::DelayWrite:Start");
+    start_time = immutable_db_options_.clock->NowMicros();
+
     if (delay > 0) {
       if (write_options.no_slowdown) {
         return Status::Incomplete("Write stall");
       }
-      start_time = immutable_db_options_.clock->NowMicros();
       TEST_SYNC_POINT("DBImpl::DelayWrite:Sleep");
 
       // Notify write_thread about the stall so it can setup a barrier and
diff --git a/unreleased_history/bug_fixes/fix_stall_counter.md b/unreleased_history/bug_fixes/fix_stall_counter.md
@@ -0,0 +1 @@
+Fix a WRITE_STALL counter that was reporting wrong value in few cases.

Original file line number	Diff line number	Diff line change
`@@ -1839,11 +1839,12 @@ Status DBImpl::DelayWrite(uint64_t num_bytes, WriteThread& write_thread,`
`1839`	`1839`	`delay = 0;`
`1840`	`1840`	`}`
`1841`	`1841`	`TEST_SYNC_POINT("DBImpl::DelayWrite:Start");`
	`1842`	`+ start_time = immutable_db_options_.clock->NowMicros();`
	`1843`	`+`
`1842`	`1844`	`if (delay > 0) {`
`1843`	`1845`	`if (write_options.no_slowdown) {`
`1844`	`1846`	`return Status::Incomplete("Write stall");`
`1845`	`1847`	`}`
`1846`		`- start_time = immutable_db_options_.clock->NowMicros();`
`1847`	`1848`	`TEST_SYNC_POINT("DBImpl::DelayWrite:Sleep");`
`1848`	`1849`
`1849`	`1850`	`// Notify write_thread about the stall so it can setup a barrier and`
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	`+Fix a WRITE_STALL counter that was reporting wrong value in few cases.`