Date: Sat, 22 Dec 2012 11:57:01 -0700 (MST) From: Ian Lepore <freebsd@damnhippie.dyndns.org> To: FreeBSD-gnats-submit@FreeBSD.org Subject: bin/174641: [patch] jemalloc enhancement: allow MI request for min-sized chunks Message-ID: <201212221857.qBMIv1MC047004@revolution.hippie.lan> Resent-Message-ID: <201212221900.qBMJ00g6043767@freefall.freebsd.org>
next in thread | raw e-mail | index | archive | help
>Number: 174641
>Category: bin
>Synopsis: [patch] jemalloc enhancement: allow MI request for min-sized chunks
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: change-request
>Submitter-Id: current-users
>Arrival-Date: Sat Dec 22 19:00:00 UTC 2012
>Closed-Date:
>Last-Modified:
>Originator: Ian Lepore <freebsd@damnhippie.dyndns.org>
>Release: FreeBSD 10.0-CURRENT arm
>Organization:
Symmetricom, Inc.
>Environment:
FreeBSD dpcur 10.0-CURRENT FreeBSD 10.0-CURRENT #2 r244488M: Fri Dec 21 11:57:58 MST 2012 root@revolution.hippie.lan:/local/build/staging/freebsd/dp10/obj/arm.arm/local/build/staging/freebsd/dp10/src/sys/DP-1001N arm
>Description:
Programs which use mlockall(2), such as watchdogd, wire down physical pages
for all allocated vmspace. jemalloc allocates large chunks of vmspace by
default for efficiency. A daemon such as watchdogd can accidentally use
up all available ram on a small embedded system unless it tunes the lg_chunk
value down as small as possible.
A problem arises because the minimum size that can be configured for the
lg_chunk option is machine-dependent (it's based on PAGE_SIZE) and it also
must be large enough to satisfy some of jemalloc's internal requirements
which can't be known by the program. The tuning must be done before the
first allocation (before entry to main()), precluding the possibilty of
using runtime logic to determine the smallest legal value.
The attached patch enhances jemalloc's handling of the lg_chunk option:
- Requesting a value of zero asks jemalloc to quietly set the chunk size
to the smallest value allowable for the hardware it's running on.
- Requesting a non-zero size smaller than the minimum will result in using
the minimum size and emitting a warning about clipping the value.
It also changes watchdogd to use this new feature.
>How-To-Repeat:
>Fix:
--- jemalloc_lgchunk.diff begins here ---
diff -r 28b12492cd58 usr.sbin/watchdogd/watchdogd.c
--- a/usr.sbin/watchdogd/watchdogd.c Fri Dec 21 11:20:58 2012 -0700
+++ b/usr.sbin/watchdogd/watchdogd.c Sat Dec 22 11:07:13 2012 -0700
@@ -71,6 +71,14 @@ static int nap = 1;
static char *test_cmd = NULL;
/*
+ * Ask malloc to map minimum-sized chunks of virtual address space at a time, so
+ * that mlockall() won't needlessly wire megabytes of unused memory into the
+ * process. This must be done using the malloc_conf string so that it gets set
+ * up before the first allocation (before entry to main()).
+ */
+const char * malloc_conf = "lg_chunk:0";
+
+/*
* Periodically pat the watchdog, preventing it from firing.
*/
int
diff -r 28b12492cd58 contrib/jemalloc/src/jemalloc.c
--- a/contrib/jemalloc/src/jemalloc.c Fri Dec 21 11:20:58 2012 -0700
+++ b/contrib/jemalloc/src/jemalloc.c Sat Dec 22 11:07:27 2012 -0700
@@ -474,9 +474,10 @@ malloc_conf_init(void)
while (*opts != '\0' && malloc_conf_next(&opts, &k, &klen, &v,
&vlen) == false) {
+#define CONF_KEY_MATCHES(n) \
+ (sizeof(n)-1 == klen && strncmp(n, k, klen) == 0)
#define CONF_HANDLE_BOOL_HIT(o, n, hit) \
- if (sizeof(n)-1 == klen && strncmp(n, k, \
- klen) == 0) { \
+ if (CONF_KEY_MATCHES(n)) { \
if (strncmp("true", v, vlen) == 0 && \
vlen == sizeof("true")-1) \
o = true; \
@@ -498,8 +499,7 @@ malloc_conf_init(void)
continue; \
}
#define CONF_HANDLE_SIZE_T(o, n, min, max) \
- if (sizeof(n)-1 == klen && strncmp(n, k, \
- klen) == 0) { \
+ if (CONF_KEY_MATCHES(n)) { \
uintmax_t um; \
char *end; \
\
@@ -519,8 +519,7 @@ malloc_conf_init(void)
continue; \
}
#define CONF_HANDLE_SSIZE_T(o, n, min, max) \
- if (sizeof(n)-1 == klen && strncmp(n, k, \
- klen) == 0) { \
+ if (CONF_KEY_MATCHES(n)) { \
long l; \
char *end; \
\
@@ -541,8 +540,7 @@ malloc_conf_init(void)
continue; \
}
#define CONF_HANDLE_CHAR_P(o, n, d) \
- if (sizeof(n)-1 == klen && strncmp(n, k, \
- klen) == 0) { \
+ if (CONF_KEY_MATCHES(n)) { \
size_t cpylen = (vlen <= \
sizeof(o)-1) ? vlen : \
sizeof(o)-1; \
@@ -557,11 +555,41 @@ malloc_conf_init(void)
* one data page in the absence of redzones, or three
* pages in the presence of redzones. In order to
* simplify options processing, fix the limit based on
- * config_fill.
+ * config_fill. The limit is based on page size and our
+ * private internal requirements, so be liberal: If the
+ * value is zero, quietly use the minimum; if it's
+ * non-zero but less than the minimum, warn and clip the
+ * value to the minimum.
*/
- CONF_HANDLE_SIZE_T(opt_lg_chunk, "lg_chunk", LG_PAGE +
- (config_fill ? 2 : 1), (sizeof(size_t) << 3) - 1)
- if (strncmp("dss", k, klen) == 0) {
+ if (CONF_KEY_MATCHES("lg_chunk")) {
+ uintmax_t min, max, um;
+ char *end;
+
+ min = LG_PAGE + (config_fill ? 2 : 1);
+ max = (sizeof(size_t) << 3) - 1;
+ set_errno(0);
+ um = malloc_strtoumax(v, &end, 0);
+ if (get_errno() != 0 || (uintptr_t)end -
+ (uintptr_t)v != vlen) {
+ malloc_conf_error(
+ "Invalid conf value",
+ k, klen, v, vlen);
+ } else if (um > max) {
+ malloc_conf_error(
+ "Out-of-range conf value",
+ k, klen, v, vlen);
+ } else if (um < min) {
+ if (um != 0)
+ malloc_conf_error(
+ "Out-of-range conf value "
+ "clipped to min",
+ k, klen, v, vlen);
+ opt_lg_chunk = min;
+ } else
+ opt_lg_chunk = um;
+ continue;
+ }
+ if (CONF_KEY_MATCHES("dss")) {
int i;
bool match = false;
for (i = 0; i < dss_prec_limit; i++) {
diff -r 28b12492cd58 contrib/jemalloc/doc/jemalloc.3
--- a/contrib/jemalloc/doc/jemalloc.3 Fri Dec 21 11:20:58 2012 -0700
+++ b/contrib/jemalloc/doc/jemalloc.3 Sat Dec 22 11:07:33 2012 -0700
@@ -653,6 +653,9 @@ is specified during configuration, in wh
"opt\&.lg_chunk" (\fBsize_t\fR) r\-
.RS 4
Virtual memory chunk size (log base 2)\&. The default chunk size is 4 MiB (2^22)\&.
+The minimum size is based on the host's page size and various internal requirements\&.
+If the requested size is zero, the minimum size is quietly used, otherwise if the requested
+size is smaller than the minimum it is clipped to the minimum and a warning is printed\&.
.RE
.PP
"opt\&.dss" (\fBconst char *\fR) r\-
--- jemalloc_lgchunk.diff ends here ---
>Release-Note:
>Audit-Trail:
>Unformatted:
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201212221857.qBMIv1MC047004>