Re: kern/45352: pty(4)/tty(4) have a 1024 bytes transfer limit

[christos%zoulas.com@localhost (Christos Zoulas)]

On Sep 9,  1:50pm, mm_lists%pulsar-zone.net@localhost (Matthew Mondor) wrote:
-- Subject: kern/45352: pty(4)/tty(4) have a 1024 bytes transfer limit

| >Number:         45352
| >Category:       kern
| >Synopsis:       pty(4)/tty(4) have a 1024 bytes transfer limit
| >Confidential:   no
| >Severity:       non-critical
| >Priority:       medium
| >Responsible:    kern-bug-people
| >State:          open
| >Class:          change-request
| >Submitter-Id:   net
| >Arrival-Date:   Fri Sep 09 13:50:00 +0000 2011
| >Originator:     Matthew Mondor
| >Release:        NetBSD 5.1_STABLE
| >Organization:
| >Environment:
| System: NetBSD behemoth.xisop 5.1_STABLE NetBSD 5.1_STABLE (GENERIC_MM) #0: 
Mon Aug 1 12:19:58 EDT 2011 
root@behemoth.xisop:/usr/obj/sys/arch/i386/compile/GENERIC_MM i386
| Architecture: i386
| Machine: i386
| >Description:
| 

Here's a patch that adds sysctl kern.tty.qsize to change this.
I have compile and run tested it, but no performance testing for pppd

christos

Index: sys/tty.h
===================================================================
RCS file: /cvsroot/src/sys/sys/tty.h,v
retrieving revision 1.88
diff -u -u -r1.88 tty.h
--- sys/tty.h   26 Jul 2011 13:14:17 -0000      1.88
+++ sys/tty.h   9 Sep 2011 16:35:27 -0000
@@ -126,6 +126,7 @@
        int     t_state;                /* Device and driver (TS*) state. */
        int     t_wopen;                /* Processes waiting for open. */
        int     t_flags;                /* Tty flags. */
+       int     t_qsize;                /* Tty character queue size */
        struct  pgrp *t_pgrp;           /* Foreground process group. */
        struct  session *t_session;     /* Enclosing session. */
        struct  selinfo t_rsel;         /* Tty read/oob select. */
@@ -162,13 +163,13 @@
 
 #define        TTMASK  15
 #define        OBUFSIZ 100
-#define        TTYHOG  1024
+#define        TTYHOG  tp->t_qsize
 
 #ifdef _KERNEL
-#define        TTMAXHIWAT      roundup(2048, CBSIZE)
-#define        TTMINHIWAT      roundup(100, CBSIZE)
-#define        TTMAXLOWAT      256
-#define        TTMINLOWAT      32
+#define        TTMAXHIWAT      roundup(tp->t_qsize << 1, CBSIZE)
+#define        TTMINHIWAT      roundup(tp->t_qsize >> 3, CBSIZE)
+#define        TTMAXLOWAT      (tp->t_qsize >> 2)
+#define        TTMINLOWAT      (tp->t_qsize >> 5)
 #endif /* _KERNEL */
 
 /* These flags are kept in t_state. */
Index: kern/tty.c
===================================================================
RCS file: /cvsroot/src/sys/kern/tty.c,v
retrieving revision 1.246
diff -u -u -r1.246 tty.c
--- kern/tty.c  26 Jul 2011 13:14:18 -0000      1.246
+++ kern/tty.c  9 Sep 2011 16:35:30 -0000
@@ -91,6 +91,7 @@
 #include <sys/intr.h>
 #include <sys/ioctl_compat.h>
 #include <sys/module.h>
+#include <sys/bitops.h>
 
 static int     ttnread(struct tty *);
 static void    ttyblock(struct tty *);
@@ -207,12 +208,41 @@
 
 static kauth_listener_t tty_listener;
 
-static struct sysctllog *kern_tkstat_sysctllog;
+#define        TTY_MINQSIZE    0x00400
+#define        TTY_MAXQSIZE    0x10000
+int tty_qsize = TTY_MINQSIZE;
+
+static int
+sysctl_kern_tty_qsize(SYSCTLFN_ARGS)
+{
+       int newsize;
+       int error;
+       struct sysctlnode node;
+       node = *rnode;
+       node.sysctl_data = &newsize;
+
+       newsize = tty_qsize;
+       error = sysctl_lookup(SYSCTLFN_CALL(&node));
+       if (error || newp == NULL)
+               return error;
+
+       newsize = 1 << ilog2(newsize);  /* Make it a power of two */ 
+
+       if (newsize < TTY_MINQSIZE || newsize > TTY_MAXQSIZE)
+               return EINVAL;
+
+       tty_qsize = newsize;
+
+       return 0;
+}
 
 static void
-sysctl_kern_tkstat_setup(void)
+sysctl_kern_tty_setup(void)
 {
+       const struct sysctlnode *rnode, *cnode;
+       struct sysctllog *kern_tkstat_sysctllog, *kern_tty_sysctllog;
 
+       kern_tkstat_sysctllog = NULL;
        sysctl_createv(&kern_tkstat_sysctllog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_NODE, "kern", NULL,
@@ -250,6 +280,19 @@
                       SYSCTL_DESCR("Number of raw tty input characters"),
                       NULL, 0, &tk_rawcc, 0,
                       CTL_KERN, KERN_TKSTAT, KERN_TKSTAT_RAWCC, CTL_EOL);
+
+       kern_tty_sysctllog = NULL;
+       sysctl_createv(&kern_tty_sysctllog, 0, NULL, &rnode,
+                      CTLFLAG_PERMANENT,
+                      CTLTYPE_NODE, "tty", NULL,
+                      NULL, 0, NULL, 0,
+                      CTL_KERN, CTL_CREATE, CTL_EOL);
+       sysctl_createv(&kern_tty_sysctllog, 0, &rnode, &cnode,
+                      CTLFLAG_PERMANENT,
+                      CTLTYPE_INT, "qsize",
+                      SYSCTL_DESCR("TTY input and output queue size"),
+                      sysctl_kern_tty_qsize, 0, &tty_qsize, 0,
+                      CTL_CREATE, CTL_EOL);
 }
 
 int
@@ -2694,15 +2737,15 @@
        tp = kmem_zalloc(sizeof(*tp), KM_SLEEP);
        callout_init(&tp->t_rstrt_ch, 0);
        callout_setfunc(&tp->t_rstrt_ch, ttrstrt, tp);
-       /* XXX: default to 1024 chars for now */
-       clalloc(&tp->t_rawq, 1024, 1);
+       tp->t_qsize = tty_qsize;
+       clalloc(&tp->t_rawq, tp->t_qsize, 1);
        cv_init(&tp->t_rawcv, "ttyraw");
        cv_init(&tp->t_rawcvf, "ttyrawf");
-       clalloc(&tp->t_canq, 1024, 1);
+       clalloc(&tp->t_canq, tp->t_qsize, 1);
        cv_init(&tp->t_cancv, "ttycan");
        cv_init(&tp->t_cancvf, "ttycanf");
        /* output queue doesn't need quoting */
-       clalloc(&tp->t_outq, 1024, 0);
+       clalloc(&tp->t_outq, tp->t_qsize, 0);
        cv_init(&tp->t_outcv, "ttyout");
        cv_init(&tp->t_outcvf, "ttyoutf");
        /* Set default line discipline. */
@@ -2817,7 +2860,7 @@
        tty_listener = kauth_listen_scope(KAUTH_SCOPE_DEVICE,
            tty_listener_cb, NULL);
 
-       sysctl_kern_tkstat_setup();
+       sysctl_kern_tty_setup();
 }
 
 /*