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Fix IO performance regression in sparc

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Replace signalfd with signal handler/pipe.  There is no way to interrupt
the CPU execution loop when a file descriptor becomes readable.  This
results in a large performance regression in sparc emulation during
bootup.
   
This patch switches us to signal handler/pipe which was originally
suggested by Ian Jackson.  The signal handler lets us interrupt the
CPU emulation loop while the write to a pipe lets us avoid the
select/signal race condition.
    
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5451 c046a42c-6fe2-441c-8c8c-71466251a162
This commit is contained in:
aliguori 2008-10-08 19:50:24 +00:00
parent 235262cf36
commit 9e472e101f
9 changed files with 53 additions and 231 deletions
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127
compatfd.c
View file

@ -1,127 +0,0 @@
/*
* signalfd/eventfd compatibility
*
* Copyright IBM, Corp. 2008
*
* Authors:
* Anthony Liguori <aliguori@us.ibm.com>
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
*
*/
#include "qemu-common.h"
#include "compatfd.h"
#include <sys/syscall.h>
#include <pthread.h>
struct sigfd_compat_info
{
sigset_t mask;
int fd;
};
static void *sigwait_compat(void *opaque)
{
struct sigfd_compat_info *info = opaque;
int err;
sigset_t all;
sigfillset(&all);
sigprocmask(SIG_BLOCK, &all, NULL);
do {
siginfo_t siginfo;
err = sigwaitinfo(&info->mask, &siginfo);
if (err == -1 && errno == EINTR) {
err = 0;
continue;
}
if (err > 0) {
char buffer[128];
size_t offset = 0;
memcpy(buffer, &err, sizeof(err));
while (offset < sizeof(buffer)) {
ssize_t len;
len = write(info->fd, buffer + offset,
sizeof(buffer) - offset);
if (len == -1 && errno == EINTR)
continue;
if (len <= 0) {
err = -1;
break;
}
offset += len;
}
}
} while (err >= 0);
return NULL;
}
static int qemu_signalfd_compat(const sigset_t *mask)
{
pthread_attr_t attr;
pthread_t tid;
struct sigfd_compat_info *info;
int fds[2];
info = malloc(sizeof(*info));
if (info == NULL) {
errno = ENOMEM;
return -1;
}
if (pipe(fds) == -1) {
free(info);
return -1;
}
memcpy(&info->mask, mask, sizeof(*mask));
info->fd = fds[1];
pthread_attr_init(&attr);
pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
pthread_create(&tid, &attr, sigwait_compat, info);
pthread_attr_destroy(&attr);
return fds[0];
}
int qemu_signalfd(const sigset_t *mask)
{
#if defined(CONFIG_signalfd)
int ret;
ret = syscall(SYS_signalfd, -1, mask, _NSIG / 8);
if (ret != -1)
return ret;
#endif
return qemu_signalfd_compat(mask);
}
int qemu_eventfd(int *fds)
{
#if defined(CONFIG_eventfd)
int ret;
ret = syscall(SYS_eventfd, 0);
if (ret >= 0) {
fds[0] = fds[1] = ret;
return 0;
}
#endif
return pipe(fds);
}