Author: Armin Rigo <ar...@tunes.org>
Branch:
Changeset: r76713:ef621d60ea13
Date: 2015-04-04 18:32 +0200
http://bitbucket.org/pypy/pypy/changeset/ef621d60ea13/
Log: Issue #2017: trying to limit the virtual address space consumption
of having tons of greenlets.
diff --git a/rpython/memory/gctransform/shadowstack.py
b/rpython/memory/gctransform/shadowstack.py
--- a/rpython/memory/gctransform/shadowstack.py
+++ b/rpython/memory/gctransform/shadowstack.py
@@ -270,15 +270,16 @@
class ShadowStackPool(object):
"""Manages a pool of shadowstacks. The MAX most recently used
- shadowstacks are fully allocated and can be directly jumped into.
+ shadowstacks are fully allocated and can be directly jumped into
+ (called "full stacks" below).
The rest are stored in a more virtual-memory-friendly way, i.e.
with just the right amount malloced. Before they can run, they
- must be copied into a full shadowstack. XXX NOT IMPLEMENTED SO FAR!
+ must be copied into a full shadowstack.
"""
_alloc_flavor_ = "raw"
root_stack_depth = 163840
- #MAX = 20 not implemented yet
+ MAX = 20
def __init__(self, gcdata):
self.unused_full_stack = llmemory.NULL
@@ -299,13 +300,21 @@
forget_current_state(), and then call restore_state_from()
or start_fresh_new_state().
"""
- self._prepare_unused_stack()
+ fresh_free_fullstack = shadowstackref.prepare_free_slot()
+ if self.unused_full_stack:
+ if fresh_free_fullstack:
+ llmemory.raw_free(fresh_free_fullstack)
+ elif fresh_free_fullstack:
+ self.unused_full_stack = fresh_free_fullstack
+ else:
+ self._prepare_unused_stack()
+ #
shadowstackref.base = self.gcdata.root_stack_base
shadowstackref.top = self.gcdata.root_stack_top
shadowstackref.context = ncontext
ll_assert(shadowstackref.base <= shadowstackref.top,
"save_current_state_away: broken shadowstack")
- #shadowstackref.fullstack = True
+ shadowstackref.attach()
#
# cannot use llop.gc_writebarrier() here, because
# we are in a minimally-transformed GC helper :-/
@@ -328,6 +337,7 @@
ll_assert(bool(shadowstackref.base), "empty shadowstackref!")
ll_assert(shadowstackref.base <= shadowstackref.top,
"restore_state_from: broken shadowstack")
+ self.unused_full_stack = shadowstackref.rebuild(self.unused_full_stack)
self.gcdata.root_stack_base = shadowstackref.base
self.gcdata.root_stack_top = shadowstackref.top
self._cleanup(shadowstackref)
@@ -343,26 +353,115 @@
shadowstackref.context = llmemory.NULL
def _prepare_unused_stack(self):
+ ll_assert(self.unused_full_stack == llmemory.NULL,
+ "already an unused_full_stack")
+ root_stack_size = sizeofaddr * self.root_stack_depth
+ self.unused_full_stack = llmemory.raw_malloc(root_stack_size)
if self.unused_full_stack == llmemory.NULL:
- root_stack_size = sizeofaddr * self.root_stack_depth
- self.unused_full_stack = llmemory.raw_malloc(root_stack_size)
- if self.unused_full_stack == llmemory.NULL:
- raise MemoryError
+ raise MemoryError
def get_shadowstackref(root_walker, gctransformer):
if hasattr(gctransformer, '_SHADOWSTACKREF'):
return gctransformer._SHADOWSTACKREF
+ # Helpers to same virtual address space by limiting to MAX the
+ # number of full shadow stacks. If there are more, we compact
+ # them into a separately-allocated zone of memory of just the right
+ # size. See the comments in the definition of fullstack_cache below.
+
+ def ll_prepare_free_slot(_unused):
+ """Free up a slot in the array of MAX entries, ready for storing
+ a new shadowstackref. Return the memory of the now-unused full
+ shadowstack.
+ """
+ index = fullstack_cache[0]
+ if index > 0:
+ return llmemory.NULL # there is already at least one free slot
+ #
+ # make a compact copy in one old entry and return the
+ # original full-sized memory
+ index = -index
+ ll_assert(index > 0, "prepare_free_slot: cache[0] == 0")
+ compacting = lltype.cast_int_to_ptr(SHADOWSTACKREFPTR,
+ fullstack_cache[index])
+ index += 1
+ if index >= ShadowStackPool.MAX:
+ index = 1
+ fullstack_cache[0] = -index # update to the next value in order
+ #
+ compacting.detach()
+ original = compacting.base
+ size = compacting.top - original
+ new = llmemory.raw_malloc(size)
+ if new == llmemory.NULL:
+ return llmemory.NULL
+ llmemory.raw_memcopy(original, new, size)
+ compacting.base = new
+ compacting.top = new + size
+ return original
+
+ def ll_attach(shadowstackref):
+ """After prepare_free_slot(), store a shadowstackref in that slot."""
+ index = fullstack_cache[0]
+ ll_assert(index > 0, "fullstack attach: no free slot")
+ fullstack_cache[0] = fullstack_cache[index]
+ fullstack_cache[index] = lltype.cast_ptr_to_int(shadowstackref)
+ ll_assert(shadowstackref.fsindex == 0, "fullstack attach: already
one?")
+ shadowstackref.fsindex = index # > 0
+
+ def ll_detach(shadowstackref):
+ """Detach a shadowstackref from the array of MAX entries."""
+ index = shadowstackref.fsindex
+ ll_assert(index > 0, "detach: unattached shadowstackref")
+ ll_assert(fullstack_cache[index] ==
+ lltype.cast_ptr_to_int(shadowstackref),
+ "detach: bad fullstack_cache")
+ shadowstackref.fsindex = 0
+ fullstack_cache[index] = fullstack_cache[0]
+ fullstack_cache[0] = index
+
+ def ll_rebuild(shadowstackref, fullstack_base):
+ if shadowstackref.fsindex > 0:
+ shadowstackref.detach()
+ return fullstack_base
+ else:
+ # make an expanded copy of the compact shadowstack stored in
+ # 'shadowstackref' and free that
+ compact = shadowstackref.base
+ size = shadowstackref.top - compact
+ shadowstackref.base = fullstack_base
+ shadowstackref.top = fullstack_base + size
+ llmemory.raw_memcopy(compact, fullstack_base, size)
+ llmemory.raw_free(compact)
+ return llmemory.NULL
+
SHADOWSTACKREFPTR = lltype.Ptr(lltype.GcForwardReference())
SHADOWSTACKREF = lltype.GcStruct('ShadowStackRef',
- ('base', llmemory.Address),
- ('top', llmemory.Address),
- ('context', llmemory.Address),
- #('fullstack', lltype.Bool),
- rtti=True)
+ ('base', llmemory.Address),
+ ('top', llmemory.Address),
+ ('context', llmemory.Address),
+ ('fsindex', lltype.Signed),
+ rtti=True,
+ adtmeths={'prepare_free_slot': ll_prepare_free_slot,
+ 'attach': ll_attach,
+ 'detach': ll_detach,
+ 'rebuild': ll_rebuild})
SHADOWSTACKREFPTR.TO.become(SHADOWSTACKREF)
+ # Items 1..MAX-1 of the following array can be SHADOWSTACKREF
+ # addresses cast to integer. Or, they are small numbers and they
+ # make up a free list, rooted in item 0, which goes on until
+ # terminated with a negative item. This negative item gives (the
+ # opposite of) the index of the entry we try to remove next.
+ # Initially all items are in this free list and the end is '-1'.
+ fullstack_cache = lltype.malloc(lltype.Array(lltype.Signed),
+ ShadowStackPool.MAX,
+ flavor='raw', immortal=True)
+ for i in range(len(fullstack_cache) - 1):
+ fullstack_cache[i] = i + 1
+ fullstack_cache[len(fullstack_cache) - 1] = -1
+
def customtrace(gc, obj, callback, arg):
obj = llmemory.cast_adr_to_ptr(obj, SHADOWSTACKREFPTR)
addr = obj.top
@@ -384,6 +483,8 @@
h = llmemory.cast_adr_to_ptr(h, _c.handle)
shadowstackref.context = llmemory.NULL
#
+ if shadowstackref.fsindex > 0:
+ shadowstackref.detach()
base = shadowstackref.base
shadowstackref.base = llmemory.NULL
shadowstackref.top = llmemory.NULL
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