From 0de3b24dc9428a37330f9065bc3626a3a07a9200 Mon Sep 17 00:00:00 2001

Message-Id: <0de3b24dc9428a37330f9065bc3626a3a07a9200.1387382496.git.minovotn@redhat.com>

In-Reply-To: <c5386144fbf09f628148101bc674e2421cdd16e3.1387382496.git.minovotn@redhat.com>

References: <c5386144fbf09f628148101bc674e2421cdd16e3.1387382496.git.minovotn@redhat.com>

From: Marcelo Tosatti <mtosatti@redhat.com>

Date: Thu, 12 Dec 2013 01:36:44 +0100

Subject: [PATCH 46/46] mempath: prefault pages manually (v4)

RH-Author: Marcelo Tosatti <mtosatti@redhat.com>

Message-id: <20131212013644.GA8646@amt.cnet>

Patchwork-id: 56243

O-Subject: [RHEL7 qemu-kvm PATCH] mempath: prefault pages manually (v4)

Bugzilla: 1026554

RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>

RH-Acked-by: Igor Mammedov <imammedo@redhat.com>

RH-Acked-by: Andrew Jones <drjones@redhat.com>

commit ef36fa1492e9105f3fa607b56edc63df513d7da1 upstream

v4: s/fail/failed/  (Peter Maydell)

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

BZ: 1026554

Signed-off-by: Michal Novotny <minovotn@redhat.com>

---

 exec.c          | 59 +++++++++++++++++++++++++++++++++++++++++++++------------

 qemu-options.hx |  2 --

 vl.c            |  4 ----

 3 files changed, 47 insertions(+), 18 deletions(-)

diff --git a/exec.c b/exec.c

index 64af205..571cea4 100644

--- a/exec.c

+++ b/exec.c

@@ -865,6 +865,13 @@ static long gethugepagesize(const char *path)

     return fs.f_bsize;

 }

+static sigjmp_buf sigjump;

+

+static void sigbus_handler(int signal)

+{

+    siglongjmp(sigjump, 1);

+}

+

 static void *file_ram_alloc(RAMBlock *block,

                             ram_addr_t memory,

                             const char *path)

@@ -874,9 +881,6 @@ static void *file_ram_alloc(RAMBlock *block,

     char *c;

     void *area;

     int fd;

-#ifdef MAP_POPULATE

-    int flags;

-#endif

     unsigned long hpagesize;

     hpagesize = gethugepagesize(path);

@@ -924,21 +928,52 @@ static void *file_ram_alloc(RAMBlock *block,

     if (ftruncate(fd, memory))

         perror("ftruncate");

-#ifdef MAP_POPULATE

-    /* NB: MAP_POPULATE won't exhaustively alloc all phys pages in the case

-     * MAP_PRIVATE is requested.  For mem_prealloc we mmap as MAP_SHARED

-     * to sidestep this quirk.

-     */

-    flags = mem_prealloc ? MAP_POPULATE | MAP_SHARED : MAP_PRIVATE;

-    area = mmap(0, memory, PROT_READ | PROT_WRITE, flags, fd, 0);

-#else

     area = mmap(0, memory, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);

-#endif

     if (area == MAP_FAILED) {

         perror("file_ram_alloc: can't mmap RAM pages");

         close(fd);

         return (NULL);

     }

+

+    if (mem_prealloc) {

+        int ret, i;

+        struct sigaction act, oldact;

+        sigset_t set, oldset;

+

+        memset(&act, 0, sizeof(act));

+        act.sa_handler = &sigbus_handler;

+        act.sa_flags = 0;

+

+        ret = sigaction(SIGBUS, &act, &oldact);

+        if (ret) {

+            perror("file_ram_alloc: failed to install signal handler");

+            exit(1);

+        }

+

+        /* unblock SIGBUS */

+        sigemptyset(&set);

+        sigaddset(&set, SIGBUS);

+        pthread_sigmask(SIG_UNBLOCK, &set, &oldset);

+

+        if (sigsetjmp(sigjump, 1)) {

+            fprintf(stderr, "file_ram_alloc: failed to preallocate pages\n");

+            exit(1);

+        }

+

+        /* MAP_POPULATE silently ignores failures */

+        for (i = 0; i < (memory/hpagesize)-1; i++) {

+            memset(area + (hpagesize*i), 0, 1);

+        }

+

+        ret = sigaction(SIGBUS, &oldact, NULL);

+        if (ret) {

+            perror("file_ram_alloc: failed to reinstall signal handler");

+            exit(1);

+        }

+

+        pthread_sigmask(SIG_SETMASK, &oldset, NULL);

+    }

+

     block->fd = fd;

     return area;

 }

diff --git a/qemu-options.hx b/qemu-options.hx

index e3c5d67..d9320b5 100644

--- a/qemu-options.hx

+++ b/qemu-options.hx

@@ -228,7 +228,6 @@ STEXI

 Allocate guest RAM from a temporarily created file in @var{path}.

 ETEXI

-#ifdef MAP_POPULATE

 DEF("mem-prealloc", 0, QEMU_OPTION_mem_prealloc,

     "-mem-prealloc   preallocate guest memory (use with -mem-path)\n",

     QEMU_ARCH_ALL)

@@ -237,7 +236,6 @@ STEXI

 @findex -mem-prealloc

 Preallocate memory when using -mem-path.

 ETEXI

-#endif

 DEF("k", HAS_ARG, QEMU_OPTION_k,

     "-k language     use keyboard layout (for example 'fr' for French)\n",

diff --git a/vl.c b/vl.c

index 0cbbdf0..da12b90 100644

--- a/vl.c

+++ b/vl.c

@@ -188,9 +188,7 @@ static int display_remote;

 const char* keyboard_layout = NULL;

 ram_addr_t ram_size;

 const char *mem_path = NULL;

-#ifdef MAP_POPULATE

 int mem_prealloc = 0; /* force preallocation of physical target memory */

-#endif

 int nb_nics;

 NICInfo nd_table[MAX_NICS];

 int autostart;

@@ -3174,11 +3172,9 @@ int main(int argc, char **argv, char **envp)

             case QEMU_OPTION_mempath:

                 mem_path = optarg;

                 break;

-#ifdef MAP_POPULATE

             case QEMU_OPTION_mem_prealloc:

                 mem_prealloc = 1;

                 break;

-#endif

             case QEMU_OPTION_d:

                 log_mask = optarg;

                 break;

-- 

1.7.11.7