For HTTP/2 we'll need some buffer-only equivalent functions to some of
the ones applying to channels and still squatting the bi_* / bo_*
namespace. Since these names have kept being misleading for quite some
time now and are really getting annoying, it's time to rename them. This
commit will use "ci/co" as the prefix (for "channel in", "channel out")
instead of "bi/bo". The following ones were renamed :
bi_getblk_nc, bi_getline_nc, bi_putblk, bi_putchr,
bo_getblk, bo_getblk_nc, bo_getline, bo_getline_nc, bo_inject,
bi_putchk, bi_putstr, bo_getchr, bo_skip, bi_swpbuf
Usually it's desirable to merge similarly sized pools, which is the
reason why their size is rounded up to the next multiple of 16. But
for the buffers this is problematic because we add the size of
struct buffer to the user-requested size, and the rounding results
in 8 extra bytes that are usable in the end. So the user gets more
bytes than asked for, and in case of SSL it results in short writes
for the extra bytes that are sent above multiples of 16 kB.
So we add a new flag MEM_F_EXACT to request that the size is not
rounded up when creating the entry. Thus it doesn't disable merging.
When DEBUG_MEMORY_POOLS is used, we now use the link pointer at the end
of the pool to store a pointer to the pool, and to control it during
pool_free2() in order to serve four purposes :
- at any instant we can know what pool an object was allocated from
when examining memory, hence how we should possibly decode it ;
- it serves to detect double free when they happen, as the pointer
cannot be valid after the element is linked into the pool ;
- it serves to detect if an element is released in the wrong pool ;
- it serves as a canary, to detect if some buffers experienced an
overflow before being release.
All these elements will definitely help better troubleshoot strange
situations, or at least confirm that certain conditions did not happen.
When debugging a core file, it's sometimes convenient to be able to
visit the released entries in the pools (typically last released
session). Unfortunately the first bytes of these entries are destroyed
by the link elements of the pool. And of course, most structures have
their most accessed elements at the beginning of the structure (typically
flags). Let's add a build-time option DEBUG_MEMORY_POOLS which allocates
an extra pointer in each pool to put the link at the end of each pool
item instead of the beginning.
When debugging an issue, sometimes it can be useful to be able to use
byte 0 to poison memory areas, resulting in the same effect as a calloc().
This patch changes the default mem_poison_byte to -1 to disable it so that
all positive values are usable.
Till now this function would only allocate one entry at a time. But with
dynamic buffers we'll like to allocate the number of missing entries to
properly refill the pool.
Let's modify it to take a minimum amount of available entries. This means
that when we know we need at least a number of available entries, we can
ask to allocate all of them at once. It also ensures that we don't move
the pointers back and forth between the caller and the pool, and that we
don't call pool_gc2() for each failed malloc. Instead, it's called only
once and the malloc is only allowed to fail once.
pool_alloc2() used to pick the entry from the pool, fall back to
pool_refill_alloc(), and to perform the poisonning itself, which
pool_refill_alloc() was also doing. While this led to optimal
code size, it imposes memory poisonning on the buffers as well,
which is extremely slow on large buffers.
This patch cuts the allocator in 3 layers :
- a layer to pick the first entry from the pool without falling back to
pool_refill_alloc() : pool_get_first()
- a layer to allocate a dirty area by falling back to pool_refill_alloc()
but never performing the poisonning : pool_alloc_dirty()
- pool_alloc2() which calls the latter and optionally poisons the area
No functional changes were made.
There's a long-standing bug in pool_gc2(). It tries to protect the pool
against releasing of too many entries but the formula is wrong as it
compares allocated to minavail instead of (allocated-used) to minavail.
Under memory contention, it ends up releasing more than what is granted
by minavail and causes trouble to the dynamic buffer allocator.
This bug is in fact major by itself, but since minavail has never been
used till now, there is no impact at least in mainline. A backport to
1.5 is desired anyway in case any future backport or out-of-tree patch
relies on this.
show pools
Dump the status of internal memory pools. This is useful to track memory
usage when suspecting a memory leak for example. It does exactly the same
as the SIGQUIT when running in foreground except that it does not flush
the pools.
From time to time, some bugs are discovered that are caused by non-initialized
memory areas. It happens that most platforms return a zero-filled area upon
first malloc() thus hiding potential bugs. This patch also replaces malloc()
in pools with calloc() to ensure that all platforms exhibit the same behaviour
upon startup. In order to catch these bugs more easily, add a -dM command line
flag to enable memory poisonning. Optionally, passing -dM<byte> forces the
poisonning byte to <byte>.
A race condition exists in the hot reconfiguration code. It is
theorically possible that the second signal is sent during a free()
in the first list, which can cause crashes or freezes (the later
have been observed). Just set up a counter to ensure we do not
recurse.
New functions implemented:
- deinit_pollers: called at the end of deinit())
- prune_acl: called via list_for_each_entry_safe
Add missing pool_destroy2 calls:
- p->hdr_idx_pool
- pool2_tree64
Implement all task stopping:
- health-check: needs new "struct task" in the struct server
- queue processing: queue_mgt
- appsess_refresh: appsession_refresh
before (idle system):
==6079== LEAK SUMMARY:
==6079== definitely lost: 1,112 bytes in 75 blocks.
==6079== indirectly lost: 53,356 bytes in 2,090 blocks.
==6079== possibly lost: 52 bytes in 1 blocks.
==6079== still reachable: 150,996 bytes in 504 blocks.
==6079== suppressed: 0 bytes in 0 blocks.
after (idle system):
==6945== LEAK SUMMARY:
==6945== definitely lost: 7,644 bytes in 137 blocks.
==6945== indirectly lost: 9,913 bytes in 587 blocks.
==6945== possibly lost: 0 bytes in 0 blocks.
==6945== still reachable: 0 bytes in 0 blocks.
==6945== suppressed: 0 bytes in 0 blocks.
before (running system for ~2m):
==9343== LEAK SUMMARY:
==9343== definitely lost: 1,112 bytes in 75 blocks.
==9343== indirectly lost: 54,199 bytes in 2,122 blocks.
==9343== possibly lost: 52 bytes in 1 blocks.
==9343== still reachable: 151,128 bytes in 509 blocks.
==9343== suppressed: 0 bytes in 0 blocks.
after (running system for ~2m):
==11616== LEAK SUMMARY:
==11616== definitely lost: 7,644 bytes in 137 blocks.
==11616== indirectly lost: 9,981 bytes in 591 blocks.
==11616== possibly lost: 0 bytes in 0 blocks.
==11616== still reachable: 4 bytes in 1 blocks.
==11616== suppressed: 0 bytes in 0 blocks.
Still not perfect but significant improvement.
since pools v2, the way pools were destroyed at exit is incorrect
because it ought to account for users of those pools before freeing
them. This test also ensures there is no double free.
When we're interrupted by another instance, it is very likely
that the other one will need some memory. Now we know how to
free what is not used, so let's do it.
Also only free non-null pointers. Previously, pool_destroy()
did implicitly check for this case which was incidentely
needed.
- keep the number of users of each pool
- call the garbage collector on out of memory conditions
- sort the pools by size for faster creation
- force the alignment size to 16 bytes instead of 4*sizeof(void *)
