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hash: prevent eleventy-gigabyte core dumps

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Add MADV_DONTDUMP to the list of advice flags.

There are now three flags which may or may not be supported by the
target kernel.  Try each one and log its success or failure separately.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>
This commit is contained in:
Zygo Blaxell 2017-01-12 22:55:08 -05:00
parent 5e91529ad2
commit 382f8bf06a
1 changed files with 14 additions and 6 deletions
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20
src/bees-hash.cc
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@ -635,12 +635,20 @@ BeesHashTable::BeesHashTable(shared_ptr<BeesContext> ctx, string filename, off_t
THROW_CHECK2(runtime_error, m_void_ptr, m_bucket_ptr, m_void_ptr == m_bucket_ptr);
THROW_CHECK2(runtime_error, m_void_ptr, m_extent_ptr, m_void_ptr == m_extent_ptr);
{
// It's OK if this fails (e.g. kernel not built with CONFIG_TRANSPARENT_HUGEPAGE)
// We don't fork any more so DONTFORK isn't really needed
BEESTOOLONG("madvise(MADV_HUGEPAGE | MADV_DONTFORK)");
if (madvise(m_byte_ptr, m_size, MADV_HUGEPAGE | MADV_DONTFORK)) {
BEESLOG("mostly harmless: madvise(MADV_HUGEPAGE | MADV_DONTFORK) failed: " << strerror(errno));
// Give all the madvise hints that the kernel understands
const struct madv_flag {
const char *name;
int value;
} madv_flags[] = {
{ .name = "MADV_HUGEPAGE", .value = MADV_HUGEPAGE },
{ .name = "MADV_DONTFORK", .value = MADV_DONTFORK },
{ .name = "MADV_DONTDUMP", .value = MADV_DONTDUMP },
{ .name = "", .value = 0 },
};
for (auto fp = madv_flags; fp->value; ++fp) {
BEESTOOLONG("madvise(" << fp->name << ")");
if (madvise(m_byte_ptr, m_size, fp->value)) {
BEESLOG("madvise(..., " << fp->name << "): " << strerror(errno) << " (ignored)");
}
}