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/*
* Copyright 2017, Red Hat, Inc.
* Author: Jeff Moyer <jmoyer@redhat.com>
* Based on test code from Mauricio Faria de Oliveira
* <mauricfo@linux.vnet.ibm.com>
* License: GPLv2
*
* Description: Ensure that aio-max-nr requests can be allocated, or,
* if not, that the reason is not faulty accounting.
*/
#include <libaio.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#define FAIL 1
#define AIO_MAX_NR "/proc/sys/fs/aio-max-nr"
#define AIO_NR "/proc/sys/fs/aio-nr"
static unsigned aio_max_nr;
int
read_proc_val(const char *path, unsigned *val)
{
FILE *fp;
int ret;
fp = fopen(path, "r");
if (!fp) {
fprintf(stderr, "Unable to open proc file \"%s\" for reading\n",
path);
return FAIL;
}
ret = fscanf(fp, "%u\n", val);
fclose(fp);
if (ret == EOF) {
fprintf(stderr, "Failed to read from proc file \"%s\"\n",
path);
return FAIL;
}
return 0;
}
/*
* Create as many ioctx-s with nr_events each as possible (up to aio_max_nr).
* Report any failures of -EAGAIN.
*/
int
do_alloc_ioctxs(int nr_events)
{
long ret;
unsigned i, avail, aio_nr, nr_ctxs;
io_context_t *ioctx;
ret = read_proc_val(AIO_NR, &aio_nr);
if (ret)
return FAIL;
avail = aio_max_nr - aio_nr;
nr_ctxs = avail / nr_events;
ioctx = calloc(nr_ctxs, sizeof(*ioctx));
if (!ioctx) {
fprintf(stderr, "allocating %u ioctx-s failed with %d\n",
nr_ctxs, errno);
return FAIL;
}
fprintf(stderr, "Creating %u ioctx-s with %u events each...\n", nr_ctxs,
nr_events);
fflush(stderr);
for (i = 0; i < nr_ctxs; i++) {
ret = io_setup(nr_events, &ioctx[i]);
if (ret) {
/*
* EAGAIN is the only failure case we're interested
* in. -ENOMEM, for example, is expected in this
* test.
*/
if (ret != -EAGAIN)
break;
fprintf(stderr,"io_setup(%u) failed on iteration %d.\n",
nr_events, i);
fprintf(stderr, "allocated %u of %u possible events.\n",
nr_events * i, aio_max_nr);
ret = read_proc_val(AIO_NR, &aio_nr);
if (ret == 0)
fprintf(stderr, "aio_nr is currently at %u\n",
aio_nr);
free(ioctx);
return FAIL;
}
}
fprintf(stderr, "Successfully created %u io_context-s\n", i);
if (i < nr_ctxs - 1)
fprintf(stderr, "Last io_setup call returned %ld (%s)\n", ret,
strerror(-ret));
fflush(stderr);
return 0;
}
/*
* We fork off a child to do the actual work. The reason is that each
* io_destroy will incur an rcu grace period to complete. That really
* adds up, depending on the number of io_contexts created. We take
* advantage of an optimization in the kernel that waits for all
* contexts to be torn down in one grace period. In other words, just
* exiting the process without tearing down the ioctx-s using
* io_destroy is way faster.
*/
int
alloc_ioctxs(int nr_events)
{
pid_t child;
int ret, status;
child = fork();
switch (child) {
case 0: /* child */
ret = do_alloc_ioctxs(nr_events);
exit(ret);
case -1:
fprintf(stderr, "fork() failed with %d\n", errno);
return FAIL;
default:
break;
}
if (waitpid(child, &status, 0) < 0)
return FAIL;
if (WIFEXITED(status) && WEXITSTATUS(status) == 0)
return 0;
return FAIL;
}
int
test_main()
{
int ret;
unsigned nr_events;
ret = read_proc_val(AIO_MAX_NR, &aio_max_nr);
if (ret)
return FAIL;
fprintf(stderr, "aio_max_nr: %u\n", aio_max_nr);
nr_events = 1;
while (1) {
ret = alloc_ioctxs(nr_events);
if (ret)
return FAIL;
if (nr_events == aio_max_nr)
break;
nr_events *= 2;
if (nr_events > aio_max_nr)
nr_events = aio_max_nr;
}
return 0;
}
/*
* Local variables:
* mode: c
* c-basic-offset: 8
* End:
*/
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