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Don't request CTLTYPE_OPAQUE if we can't print them.

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The intent is to skip expensive opaque sysctls like tcp_pcblist unless
they are explicitly requested. Sysctl nodes like this don't show up in
sysctl -a, but they do generate output that winds up being dropped,
unless the user specifically requested  binary/hex output or opaques.

This reduces the runtime of sysctl in many circumstances on a loaded
system.  It also reduces the likelihood that simply gathering
diagnostics on a sick machine (stuck lock, etc) via sysctl -a might
push it over the edge into a total lockup.

Reviewed by:	jtl
Sponsored by:	Netflix
Differential Revision:	https://reviews.freebsd.org/D11461
This commit is contained in:
gallatin 2017-07-31 14:56:35 +00:00
parent a535821da5
commit c10cdb0dac
1 changed files with 26 additions and 18 deletions
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44
sbin/sysctl/sysctl.c
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@ -925,6 +925,32 @@ show_var(int *oid, int nlen)
printf("%s", buf);
return (0);
}
/* don't fetch opaques that we don't know how to print */
if (ctltype == CTLTYPE_OPAQUE) {
if (strcmp(fmt, "S,clockinfo") == 0)
func = S_clockinfo;
else if (strcmp(fmt, "S,timeval") == 0)
func = S_timeval;
else if (strcmp(fmt, "S,loadavg") == 0)
func = S_loadavg;
else if (strcmp(fmt, "S,vmtotal") == 0)
func = S_vmtotal;
#ifdef __amd64__
else if (strcmp(fmt, "S,efi_map_header") == 0)
func = S_efi_map;
#endif
#if defined(__amd64__) || defined(__i386__)
else if (strcmp(fmt, "S,bios_smap_xattr") == 0)
func = S_bios_smap_xattr;
#endif
else {
func = NULL;
if (!bflag && !oflag && !xflag)
return (1);
}
}
/* find an estimate of how much we need for this var */
if (Bflag)
j = Bflag;
@ -1045,24 +1071,6 @@ show_var(int *oid, int nlen)
case CTLTYPE_OPAQUE:
i = 0;
if (strcmp(fmt, "S,clockinfo") == 0)
func = S_clockinfo;
else if (strcmp(fmt, "S,timeval") == 0)
func = S_timeval;
else if (strcmp(fmt, "S,loadavg") == 0)
func = S_loadavg;
else if (strcmp(fmt, "S,vmtotal") == 0)
func = S_vmtotal;
#ifdef __amd64__
else if (strcmp(fmt, "S,efi_map_header") == 0)
func = S_efi_map;
#endif
#if defined(__amd64__) || defined(__i386__)
else if (strcmp(fmt, "S,bios_smap_xattr") == 0)
func = S_bios_smap_xattr;
#endif
else
func = NULL;
if (func) {
if (!nflag)
printf("%s%s", name, sep);