git: 12ce9e4868d1 - stable/12 - tcp: drain tcp_hostcache_list in between per-bucket locks

[Richard Scheffenegger]

The branch stable/12 has been updated by rscheff:

URL: https://cgit.FreeBSD.org/src/commit/?id=12ce9e4868d1454b263a2330ce95e91b145c1c8f

commit 12ce9e4868d1454b263a2330ce95e91b145c1c8f
Author:     Richard Scheffenegger <rscheff at FreeBSD.org>
AuthorDate: 2021-03-31 17:24:01 +0000
Commit:     Richard Scheffenegger <rscheff at FreeBSD.org>
CommitDate: 2021-04-16 20:52:09 +0000

    tcp: drain tcp_hostcache_list in between per-bucket locks
    
    Explicitly drain the sbuf after completing each hash bucket
    to minimize the work performed while holding the hash
    bucket lock.
    
    PR:             254333
    MFC after:      2 weeks
    Reviewed By:    tuexen, jhb, #transport
    Sponsored by:   NetApp, Inc.
    Differential Revision: https://reviews.freebsd.org/D29483
    
    (cherry picked from commit 869880463cc2ce64e2e6599eaec880a981f3ced6)
---
 sys/netinet/tcp_hostcache.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/sys/netinet/tcp_hostcache.c b/sys/netinet/tcp_hostcache.c
index 6dfe3941c9d8..db68fd5de90d 100644
--- a/sys/netinet/tcp_hostcache.c
+++ b/sys/netinet/tcp_hostcache.c
@@ -646,12 +646,13 @@ sysctl_tcp_hc_list(SYSCTL_HANDLER_ARGS)
 		return(error);
 	}
 
-	/* Use a buffer for 16 lines */
-	sbuf_new_for_sysctl(&sb, NULL, 16 * linesize, req);
+	/* Use a buffer sized for one full bucket */
+	sbuf_new_for_sysctl(&sb, NULL, V_tcp_hostcache.bucket_limit * linesize, req);
 
 	sbuf_printf(&sb,
 		"\nIP address        MTU  SSTRESH      RTT   RTTVAR "
 		"    CWND SENDPIPE RECVPIPE HITS  UPD  EXP\n");
+	sbuf_drain(&sb);
 
 #define msec(u) (((u) + 500) / 1000)
 	for (i = 0; i < V_tcp_hostcache.hashsize; i++) {
@@ -682,6 +683,7 @@ sysctl_tcp_hc_list(SYSCTL_HANDLER_ARGS)
 			    hc_entry->rmx_expire);
 		}
 		THC_UNLOCK(&V_tcp_hostcache.hashbase[i].hch_mtx);
+		sbuf_drain(&sb);
 	}
 #undef msec
 	error = sbuf_finish(&sb);