OPTIM/MINOR: make it possible to change pipe size (tune.pipesize)

By default, pipes are the default size for the system. But sometimes when
using TCP splicing, it can improve performance to increase pipe sizes,
especially if it is suspected that pipes are not filled and that many
calls to splice() are performed. This has an impact on the kernel's
memory footprint, so this must not be changed if impacts are not understood.

doc/configuration.txt

@@ -461,6 +461,7 @@ The following keywords are supported in the "global" section :
    - tune.maxaccept
    - tune.maxpollevents
    - tune.maxrewrite
+   - tune.pipesize
    - tune.rcvbuf.client
    - tune.rcvbuf.server
    - tune.sndbuf.client
@@ -753,6 +754,14 @@ tune.maxrewrite <number>
   larger than that. This means you don't have to worry about it when changing
   bufsize.
 
+tune.pipesize <number>
+  Sets the kernel pipe buffer size to this size (in bytes). By default, pipes
+  are the default size for the system. But sometimes when using TCP splicing,
+  it can improve performance to increase pipe sizes, especially if it is
+  suspected that pipes are not filled and that many calls to splice() are
+  performed. This has an impact on the kernel's memory footprint, so this must
+  not be changed if impacts are not understood.
+
 tune.rcvbuf.client <number>
 tune.rcvbuf.server <number>
   Forces the kernel socket receive buffer size on the client or the server side

include/common/compat.h

@@ -69,6 +69,11 @@
 #define MAXPATHLEN 128
 #endif
 
+/* On Linux, allows pipes to be resized */
+#ifndef F_SETPIPE_SZ
+#define F_SETPIPE_SZ (1024 + 7)
+#endif
+
 #if defined(TPROXY) && defined(NETFILTER)
 #include <linux/types.h>
 #include <linux/netfilter_ipv6.h>

include/types/global.h

@@ -96,6 +96,7 @@ struct global {
 		int server_sndbuf; /* set server sndbuf to this value if not null */
 		int server_rcvbuf; /* set server rcvbuf to this value if not null */
 		int chksize;       /* check buffer size in bytes, defaults to BUFSIZE */
+		int pipesize;      /* pipe size in bytes, system defaults if zero */
 	} tune;
 	struct {
 		char *prefix;           /* path prefix of unix bind socket */

src/cfgparse.c

@@ -587,6 +587,14 @@ int cfg_parse_global(const char *file, int linenum, char **args, int kwm)
 		}
 		global.tune.server_sndbuf = atol(args[1]);
 	}
+	else if (!strcmp(args[0], "tune.pipesize")) {
+		if (*(args[1]) == 0) {
+			Alert("parsing [%s:%d] : '%s' expects an integer argument.\n", file, linenum, args[0]);
+			err_code |= ERR_ALERT | ERR_FATAL;
+			goto out;
+		}
+		global.tune.pipesize = atol(args[1]);
+	}
 	else if (!strcmp(args[0], "uid")) {
 		if (global.uid != 0) {
 			Alert("parsing [%s:%d] : user/uid already specified. Continuing.\n", file, linenum);

src/pipe.c

@@ -58,6 +58,10 @@ struct pipe *get_pipe()
 		pool_free2(pool2_pipe, ret);
 		return NULL;
 	}
+#ifdef F_SETPIPE_SZ
+	if (global.tune.pipesize)
+		fcntl(pipefd[0], F_SETPIPE_SZ, global.tune.pipesize);
+#endif
 	ret->data = 0;
 	ret->prod = pipefd[1];
 	ret->cons = pipefd[0];