[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-devel] [PATCH] blockjob: Don't sleep too short
From: |
Fam Zheng |
Subject: |
[Qemu-devel] [PATCH] blockjob: Don't sleep too short |
Date: |
Mon, 6 Jul 2015 11:28:11 +0800 |
block_job_sleep_ns is called by block job coroutines to yield the
execution to VCPU threads and monitor etc. It is pointless to sleep for
0 or a few nanoseconds, because that equals to a "yield + enter" with no
intermission in between (the timer fires immediately in the same
iteration of event loop), which means other code still doesn't get a
fair share of main loop / BQL.
Trim the sleep duration with a minimum value.
Reported-by: Alexandre DERUMIER <address@hidden>
Signed-off-by: Fam Zheng <address@hidden>
---
blockjob.c | 2 ++
include/block/blockjob.h | 4 +++-
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/blockjob.c b/blockjob.c
index ec46fad..b17ed1f 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -238,6 +238,8 @@ void block_job_sleep_ns(BlockJob *job, QEMUClockType type,
int64_t ns)
return;
}
+ ns = MAX(ns, BLOCK_JOB_SLEEP_NS_MIN);
+
job->busy = false;
if (block_job_is_paused(job)) {
qemu_coroutine_yield();
diff --git a/include/block/blockjob.h b/include/block/blockjob.h
index 57d8ef1..3deb731 100644
--- a/include/block/blockjob.h
+++ b/include/block/blockjob.h
@@ -146,11 +146,13 @@ void *block_job_create(const BlockJobDriver *driver,
BlockDriverState *bs,
int64_t speed, BlockCompletionFunc *cb,
void *opaque, Error **errp);
+#define BLOCK_JOB_SLEEP_NS_MIN 10000000L
/**
* block_job_sleep_ns:
* @job: The job that calls the function.
* @clock: The clock to sleep on.
- * @ns: How many nanoseconds to stop for.
+ * @ns: How many nanoseconds to stop for. It sleeps at least
+ * for BLOCK_JOB_SLEEP_NS_MIN ns, even if a smaller value is specified.
*
* Put the job to sleep (assuming that it wasn't canceled) for @ns
* nanoseconds. Canceling the job will interrupt the wait immediately.
--
2.4.3
- [Qemu-devel] [PATCH] blockjob: Don't sleep too short,
Fam Zheng <=