concurrent invocations from acquiring the same address(es). Also, in case
of an incomplete allocation, free any allocated pages.
In collaboration with: tegge
sure that uma_dbg_free() is called if we're about to call
uma_zfree_internal() but we're asking it to skip the dtor and
uma_dbg_free() call itself. So, if we're about to call
uma_zfree_internal() from uma_zfree_arg() and skip == 1, call
uma_dbg_free() ourselves.
1) The race has to do with zone destruction. From the zone destructor we
would lock the zone, set the working set size to 0, then unlock the zone,
drain it, and then free the structure. Within the window following the
working-set-size set to 0 and unlocking of the zone and the point where
in zone_drain we re-acquire the zone lock, the uma timer routine could
have fired off and changed the working set size to something non-zero,
thereby potentially preventing us from completely freeing slabs before
destroying the zone (and thus leaking them).
2) The leak has to do with zone destruction as well. When destroying a
zone we would take care to free all the buckets cached in the zone, but
although we would drain the pcpu cache buckets, we would not free them.
This resulted in leaking a couple of bucket structures (512 bytes each)
per cpu on SMP during zone destruction.
While I'm here, also silence GCC warnings by turning uma_slab_alloc()
from inline to real function. It's too big to be an inline.
Reviewed by: JeffR
("UMA Zone") carefully, because it does not have pcpu caches allocated
at all. In the UP case, we did not catch this because one pcpu cache
is always allocated with the zone, but for the MP case, we were getting
bogus stats for this zone.
Tested by: Lukas Ertl <le@univie.ac.at>
- In sysctl_vm_zone use the per cpu locks to read the current cache
statistics this makes them more accurate while under heavy load.
Submitted by: tegge
so not only wastes memory but it can also cause a leak in zones that
will be destroyed later. The problem is that the slab allocation code
places newly created slabs on the partially allocated list because it
assumes that the caller will actually allocate some memory from it.
Failure to do so places an otherwise free slab on the partial slab list
where we wont find it later in zone_drain().
Continuously prodded to fix by: phk (Thanks)
uma_zalloc) is called with exactly one of either M_WAITOK or M_NOWAIT and
that it is called with neither M_TRYWAIT or M_DONTWAIT. Print a warning
if anything is wrong. Default to M_WAITOK of no flag is given. This is the
same test as in malloc(9).
of pcpu locks. This makes uma_zone somewhat smaller (by (LOCKNAME_LEN *
sizeof(char) + sizeof(struct mtx) * maxcpu) bytes, to be exact).
No Objections from jeff.
extra function calls. Refactor uma_zalloc_internal into seperate functions
for finding the most appropriate slab, filling buckets, allocating single
items, and pulling items off of slabs. This makes the code significantly
cleaner.
- This also fixes the "Returning an empty bucket." panic that a few people
have seen.
Tested On: alpha, x86
held. This avoids a lock order reversal when destroying zones.
Unfortunately, this also means that the free checks are not done before
the destructor is called.
Reported by: phk
- Remove all instances of the mallochash.
- Stash the slab pointer in the vm page's object pointer when allocating from
the kmem_obj.
- Use the overloaded object pointer to find slabs for malloced memory.
allocator.
- Properly set M_ZERO when talking to the back end page allocators for
non malloc zones. This forces us to zero fill pages when they are first
brought into a cache.
- Properly handle M_ZERO in uma_zalloc_internal. This fixes a problem where
per cpu buckets weren't always getting zeroed.
allocated slabs and bucket caches for free items. It will not go ask the vm
for pages. This differs from M_NOWAIT in that it not only doesn't block, it
doesn't even ask.
- Add a new zcreate option ZONE_VM, that sets the BUCKETCACHE zflag. This
tells uma that it should only allocate buckets out of the bucket cache, and
not from the VM. It does this by using the M_NOVM option to zalloc when
getting a new bucket. This is so that the VM doesn't recursively enter
itself while trying to allocate buckets for vm_map_entry zones. If there
are already allocated buckets when we get here we'll still use them but
otherwise we'll skip it.
- Use the ZONE_VM flag on vm map entries and pv entries on x86.
that td_intr_nesting_level is 0 (like malloc() does). Since malloc() calls
uma we can probably remove the check in malloc() for this now. Also,
perform an extra witness check in that case to make sure we don't hold
any locks when performing a M_WAITOK allocation.
several reasons before. Fixing it involved restructuring the generic hash
code to require calling code to handle locking, unlocking, and freeing hashes
on error conditions.
