3cd55d49a
Jan Klötzke
2020-11-22
Subject
mdev: increase netlink buffer sizes
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util-linux/mdev.c+17 -9
| @@ -269,10 +269,6 @@ | |
| # define dbg3s(msg) ((void)0) | |
| #endif | |
| - | |
| - | #ifndef SO_RCVBUFFORCE |
| - | #define SO_RCVBUFFORCE 33 |
| - | #endif |
| static const char keywords[] ALIGN1 = "add\0remove\0"; // "change\0" | |
| enum { OP_add, OP_remove }; | |
| @@ -1152,15 +1148,27 @@ static void initial_scan(char *temp) | |
| #if ENABLE_FEATURE_MDEV_DAEMON | |
| - | /* uevent applet uses 16k buffer, and mmaps it before every read */ |
| - | # define BUFFER_SIZE (2 * 1024) |
| - | # define RCVBUF (2 * 1024 * 1024) |
| + | /* |
| + | * The kernel (as of v5.4) will pass up to 32 environment variables with a |
| + | * total of 2kiB on each event. On top of that the action string and device |
| + | * path are added. Using a 3kiB buffer for the event should suffice in any |
| + | * case. |
| + | * |
| + | * As far as the socket receive buffer size is concerned 2MiB proved to be too |
| + | * small (see [1]). Udevd seems to use a whooping 128MiB. The socket receive |
| + | * buffer size is just a resource limit. The buffers are allocated lazily so |
| + | * the memory is not wasted. |
| + | * |
| + | * [1] http://lists.busybox.net/pipermail/busybox/2019-December/087665.html |
| + | */ |
| + | # define USER_RCVBUF (3 * 1024) |
| + | # define KERN_RCVBUF (128 * 1024 * 1024) |
| # define MAX_ENV 32 | |
| static void daemon_loop(char *temp, int fd) | |
| { | |
| for (;;) { | |
| - | char netbuf[BUFFER_SIZE]; |
| + | char netbuf[USER_RCVBUF]; |
| char *env[MAX_ENV]; | |
| char *s, *end; | |
| ssize_t len; | |
| @@ -1237,7 +1245,7 @@ int mdev_main(int argc UNUSED_PARAM, char **argv) | |
| * mdev -d | |
| * find /sys -name uevent -exec sh -c 'echo add >"{}"' ';' | |
| */ | |
| - | fd = create_and_bind_to_netlink(NETLINK_KOBJECT_UEVENT, 1 << 0, RCVBUF); |
| + | fd = create_and_bind_to_netlink(NETLINK_KOBJECT_UEVENT, 1 << 0, KERN_RCVBUF); |
| /* | |
| * Make inital scan after the uevent socket is alive and | |