143 lines
3.5 KiB
C
143 lines
3.5 KiB
C
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// SPDX-License-Identifier: LGPL-2.1-or-later
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/*
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* Copyright (C) 2005-2006 David Gibson & Adam Litke, IBM Corporation.
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* Author: David Gibson & Adam Litke
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*/
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/*\
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* [Description]
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*
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* Some kernel versions after hugepage demand allocation was added used a
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* dubious heuristic to check if there was enough hugepage space available
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* for a given mapping. The number of not-already-instantiated pages in
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* the mapping was compared against the total hugepage free pool. It was
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* very easy to confuse this heuristic into overcommitting by allocating
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* hugepage memory in chunks, each less than the total available pool size
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* but together more than available. This would generally lead to OOM
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* SIGKILLs of one process or another when it tried to instantiate pages
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* beyond the available pool.
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*/
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#define _GNU_SOURCE
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/mount.h>
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#include <limits.h>
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#include <sys/param.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <signal.h>
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#include "hugetlb.h"
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#define MNTPOINT "hugetlbfs/"
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#define WITH_OVERCOMMIT 0
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#define WITHOUT_OVERCOMMIT 1
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static long hpage_size;
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static int huge_fd = -1;
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static void test_chunk_overcommit(void)
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{
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unsigned long totpages, chunk1, chunk2;
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void *p, *q;
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pid_t child;
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int status;
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totpages = SAFE_READ_MEMINFO(MEMINFO_HPAGE_FREE);
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chunk1 = (totpages / 2) + 1;
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chunk2 = totpages - chunk1 + 1;
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tst_res(TINFO, "Free: %ld hugepages available: "
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"chunk1=%ld chunk2=%ld", totpages, chunk1, chunk2);
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p = SAFE_MMAP(NULL, chunk1*hpage_size, PROT_READ|PROT_WRITE, MAP_SHARED,
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huge_fd, 0);
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q = mmap(NULL, chunk2*hpage_size, PROT_READ|PROT_WRITE, MAP_SHARED,
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huge_fd, chunk1*hpage_size);
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if (q == MAP_FAILED) {
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if (errno != ENOMEM) {
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tst_res(TFAIL | TERRNO, "mmap() chunk2");
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goto cleanup1;
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} else {
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tst_res(TPASS, "Successful without overcommit pages");
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goto cleanup1;
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}
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}
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tst_res(TINFO, "Looks like we've overcommitted, testing...");
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/* Looks like we're overcommited, but we need to confirm that
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* this is bad. We touch it all in a child process because an
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* overcommit will generally lead to a SIGKILL which we can't
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* handle, of course.
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*/
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child = SAFE_FORK();
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if (child == 0) {
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memset(p, 0, chunk1*hpage_size);
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memset(q, 0, chunk2*hpage_size);
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exit(0);
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}
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SAFE_WAITPID(child, &status, 0);
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if (WIFSIGNALED(status)) {
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tst_res(TFAIL, "Killed by signal '%s' due to overcommit",
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tst_strsig(WTERMSIG(status)));
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goto cleanup2;
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}
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tst_res(TPASS, "Successful with overcommit pages");
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cleanup2:
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SAFE_MUNMAP(q, chunk2*hpage_size);
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cleanup1:
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SAFE_MUNMAP(p, chunk1*hpage_size);
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SAFE_FTRUNCATE(huge_fd, 0);
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}
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static void run_test(unsigned int test_type)
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{
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switch (test_type) {
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case WITHOUT_OVERCOMMIT:
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tst_res(TINFO, "Without overcommit testing...");
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SAFE_FILE_PRINTF(PATH_OC_HPAGES, "%d", 0);
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break;
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case WITH_OVERCOMMIT:
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tst_res(TINFO, "With overcommit testing...");
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SAFE_FILE_PRINTF(PATH_OC_HPAGES, "%d", 2);
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break;
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}
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test_chunk_overcommit();
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}
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static void setup(void)
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{
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hpage_size = SAFE_READ_MEMINFO(MEMINFO_HPAGE_SIZE)*1024;
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huge_fd = tst_creat_unlinked(MNTPOINT, 0);
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}
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static void cleanup(void)
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{
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SAFE_CLOSE(huge_fd);
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}
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static struct tst_test test = {
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.needs_root = 1,
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.mntpoint = MNTPOINT,
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.needs_hugetlbfs = 1,
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.forks_child = 1,
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.save_restore = (const struct tst_path_val[]) {
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{PATH_OC_HPAGES, NULL, TST_SR_TCONF},
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{}
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},
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.tcnt = 2,
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.setup = setup,
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.cleanup = cleanup,
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.test = run_test,
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.hugepages = {3, TST_NEEDS},
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};
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