From 02dea0875b0f9b331a65fd6097dfd6115ca4ef24 Mon Sep 17 00:00:00 2001 From: Jeff Dike Date: Fri, 31 Mar 2006 02:30:08 -0800 Subject: [PATCH] UML: Hotplug memory, take 2 Changes since first version added check for MADV_REMOVE support on the host fixed error return botch shrunk sprintf array by one character This adds hotplug memory support to UML. The mconsole syntax is config mem=[+-]n[KMG] In other words, add or subtract some number of kilobytes, megabytes, or gigabytes. Unplugged pages are allocated and then madvise(MADV_TRUNCATE), which is a currently experimental madvise extension. These pages are tracked so they can be plugged back in later if the admin decides to give them back. The first page to be unplugged is used to keep track of about 4M of other pages. A list_head is the first thing on this page. The rest is filled with addresses of other unplugged pages. This first page is not madvised, obviously. When this page is filled, the next page is used in a similar way and linked onto a list with the first page. Etc. This whole process reverses when pages are plugged back in. When a tracking page no longer tracks any unplugged pages, then it is next in line for plugging, which is done by freeing pages back to the kernel. Signed-off-by: Jeff Dike Cc: Paolo 'Blaisorblade' Giarrusso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/um/os-Linux/process.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) (limited to 'arch/um/os-Linux/process.c') diff --git a/arch/um/os-Linux/process.c b/arch/um/os-Linux/process.c index d261888f39c4..8176b0b52047 100644 --- a/arch/um/os-Linux/process.c +++ b/arch/um/os-Linux/process.c @@ -11,6 +11,7 @@ #include #include #include +#include #include "ptrace_user.h" #include "os.h" #include "user.h" @@ -20,6 +21,7 @@ #include "kern_util.h" #include "longjmp.h" #include "skas_ptrace.h" +#include "kern_constants.h" #define ARBITRARY_ADDR -1 #define FAILURE_PID -1 @@ -187,6 +189,48 @@ int os_unmap_memory(void *addr, int len) return(0); } +#ifndef MADV_REMOVE +#define MADV_REMOVE 0x5 /* remove these pages & resources */ +#endif + +int os_drop_memory(void *addr, int length) +{ + int err; + + err = madvise(addr, length, MADV_REMOVE); + if(err < 0) + err = -errno; + return err; +} + +int can_drop_memory(void) +{ + void *addr; + int fd; + + printk("Checking host MADV_REMOVE support..."); + fd = create_mem_file(UM_KERN_PAGE_SIZE); + if(fd < 0){ + printk("Creating test memory file failed, err = %d\n", -fd); + return 0; + } + + addr = mmap64(NULL, UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE, + MAP_PRIVATE, fd, 0); + if(addr == MAP_FAILED){ + printk("Mapping test memory file failed, err = %d\n", -errno); + return 0; + } + + if(madvise(addr, UM_KERN_PAGE_SIZE, MADV_REMOVE) != 0){ + printk("MADV_REMOVE failed, err = %d\n", -errno); + return 0; + } + + printk("OK\n"); + return 1; +} + void init_new_thread_stack(void *sig_stack, void (*usr1_handler)(int)) { int flags = 0, pages; -- cgit v1.2.2