On 2020/5/14 23:42, Hillf Danton wrote:
On Thu, 14 May 2020 13:12:18 +0800 Rong Chen wrote:
On 5/14/20 12:27 PM, Christian Kujau wrote:
On Tue, 12 May 2020, kernel test robot wrote:
FYI, we noticed a -71.8% regression of netperf.Throughput_total_tps due to
commit:
As noted in this report, netperf is used to "measure various aspect of
networking performance". Are we sure the bisect is correct? JFS is a
filesystem and is not touching net/ in any way. So, having not attempted
to reproduce this, maybe the JFS commit is a red herring?
C.
Hi,
The commit also causes -74.6% regression of will-it-scale.per_thread_ops:
in testcase: will-it-scale
on test machine: 8 threads Intel(R) Core(TM) i7-3770K CPU @ 3.50GHz with 16G
memory
with following parameters:
nr_task: 100%
mode: thread
test: unlink2
cpufreq_governor: performance
ucode: 0x21
I'll send another report for this regression.
Best Regards,
Rong Chen
Hi
Would it make sense in terms of making robot and fuzzer happy to replace
spin lock with memory barrier, say the changes below?
Hillf
--- a/fs/jfs/jfs_txnmgr.c
+++ b/fs/jfs/jfs_txnmgr.c
@@ -416,6 +416,7 @@ tid_t txBegin(struct super_block *sb, in
* memset(tblk, 0, sizeof(struct tblock));
*/
tblk->next = tblk->last = tblk->xflag = tblk->flag = tblk->lsn = 0;
+ smp_wmb(); /* match mb in txLazyCommit() */
tblk->sb = sb;
++log->logtid;
@@ -2683,10 +2684,16 @@ static void txLazyCommit(struct tblock *
{
struct jfs_log *log;
- while (((tblk->flag & tblkGC_READY) == 0) &&
- ((tblk->flag & tblkGC_UNLOCKED) == 0)) {
- /* We must have gotten ahead of the user thread
-*/
+ for (;;) {
+ u16 flag = tblk->flag;
+
+ smp_rmb(); /* match mb in txBegin() */
+ if (flag & tblkGC_READY)
+ break;
+ if (flag & tblkGC_UNLOCKED)
+ break;
+
+ /* We must have gotten ahead of the user thread */
jfs_info("jfs_lazycommit: tblk 0x%p not unlocked", tblk);
yield();
}
@@ -2698,9 +2705,9 @@ static void txLazyCommit(struct tblock *
log = (struct jfs_log *) JFS_SBI(tblk->sb)->log;
spin_lock_irq(>gclock); // LOGGC_LOCK
-
+ smp_mb__after_spinlock();
tblk->flag |= tblkGC_COMMITTED;
-
+ smp_wmb();
if (tblk->flag & tblkGC_READY)
log->gcrtc--;
I think this patch is okay.
Thanks a lot, Hillf :)
Best wishes,
Jia-Ju Bai
