Re: [LKP] [lkp] [sctp] a6c2f79287: netperf.Throughput_Mbps -37.2% regression

[Xin Long]

>
> It doesn't seem memory is an issue.
>
> The whole dump is about the same.
> The MemFree and MemAvailable doesn't change much.
>
Hi, Aaron

1)
I talked with Marcelo about this one.
He said it might be related with cacheline.  the  new field distroyed
the prior cacheline. So on top of commit 826d253d57b1, pls only add
+       unsigned long prsctp_param;

to the end of struct sctp_chunk, then try.


2)
if 1) still doesn't work, I may think about to drop prsctp_param in
sctp_chunk, and reuse msg->expire_at. as for sent_count, I will
put it to the mem hole of sctp_chunk.

So pls also try the attachment patch,  on top of commit a6c2f792873a

Thanks.
diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 6bcda71..008cb76 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -524,7 +524,11 @@ struct sctp_datamsg {
 	struct list_head chunks;
 	/* Reference counting. */
 	atomic_t refcnt;
-	/* When is this message no longer interesting to the peer? */
+	/* Re-use this field to record param for prsctp policies,
+	 * for TTL policy, it is the time_to_drop of this chunk,
+	 * for RTX policy, it is the max_sent_count of this chunk,
+	 * for PRIO policy, it is the priority of this chunk.
+	 */
 	unsigned long expires_at;
 	/* Did the messenge fail to send? */
 	int send_error;
@@ -553,6 +557,9 @@ struct sctp_chunk {
 
 	atomic_t refcnt;
 
+	/* How many times this chunk have been sent, for prsctp RTX policy */
+	int sent_count;
+
 	/* This is our link to the per-transport transmitted list.  */
 	struct list_head transmitted_list;
 
@@ -602,16 +609,6 @@ struct sctp_chunk {
 	/* This needs to be recoverable for SCTP_SEND_FAILED events. */
 	struct sctp_sndrcvinfo sinfo;
 
-	/* We use this field to record param for prsctp policies,
-	 * for TTL policy, it is the time_to_drop of this chunk,
-	 * for RTX policy, it is the max_sent_count of this chunk,
-	 * for PRIO policy, it is the priority of this chunk.
-	 */
-	unsigned long prsctp_param;
-
-	/* How many times this chunk have been sent, for prsctp RTX policy */
-	int sent_count;
-
 	/* Which association does this belong to?  */
 	struct sctp_association *asoc;
 
diff --git a/net/sctp/chunk.c b/net/sctp/chunk.c
index 2698d12..0c53d64 100644
--- a/net/sctp/chunk.c
+++ b/net/sctp/chunk.c
@@ -349,7 +349,7 @@ int sctp_chunk_abandoned(struct sctp_chunk *chunk)
 	}
 
 	if (SCTP_PR_TTL_ENABLED(chunk->sinfo.sinfo_flags) &&
-	    time_after(jiffies, chunk->prsctp_param)) {
+	    time_after(jiffies, chunk->msg->expires_at)) {
 		if (chunk->sent_count)
 			chunk->asoc->abandoned_sent[SCTP_PR_INDEX(TTL)]++;
 		else
diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 2c431ee..c7110a9 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -718,7 +718,7 @@ static void sctp_set_prsctp_policy(struct sctp_chunk *chunk,
 		return;
 
 	if (SCTP_PR_TTL_ENABLED(sinfo->sinfo_flags))
-		chunk->prsctp_param =
+		chunk->msg->expires_at =
 			jiffies + msecs_to_jiffies(sinfo->sinfo_timetolive);
 }