Generalize chunk management hooks.

Add the "arena.<i>.chunk_hooks" mallctl, which replaces and expands on
the "arena.<i>.chunk.{alloc,dalloc,purge}" mallctls.  The chunk hooks
allow control over chunk allocation/deallocation, decommit/commit,
purging, and splitting/merging, such that the application can rely on
jemalloc's internal chunk caching and retaining functionality, yet
implement a variety of chunk management mechanisms and policies.

Merge the chunks_[sz]ad_{mmap,dss} red-black trees into
chunks_[sz]ad_retained.  This slightly reduces how hard jemalloc tries
to honor the dss precedence setting; prior to this change the precedence
setting was also consulted when recycling chunks.

Fix chunk purging.  Don't purge chunks in arena_purge_stashed(); instead
deallocate them in arena_unstash_purged(), so that the dirty memory
linkage remains valid until after the last time it is used.

This resolves #176 and #201.

1 files changed, 167 insertions, 0 deletions

diff --git a/src/pages.c b/src/pages.c
new file mode 100644
index 0000000..6f775dc
--- /dev/null
+++ b/src/pages.c
@@ -0,0 +1,167 @@
+#define	JEMALLOC_PAGES_C_
+#include "jemalloc/internal/jemalloc_internal.h"
+
+/******************************************************************************/
+
+void *
+pages_map(void *addr, size_t size)
+{
+	void *ret;
+
+	assert(size != 0);
+
+#ifdef _WIN32
+	/*
+	 * If VirtualAlloc can't allocate at the given address when one is
+	 * given, it fails and returns NULL.
+	 */
+	ret = VirtualAlloc(addr, size, MEM_COMMIT | MEM_RESERVE,
+	    PAGE_READWRITE);
+#else
+	/*
+	 * We don't use MAP_FIXED here, because it can cause the *replacement*
+	 * of existing mappings, and we only want to create new mappings.
+	 */
+	ret = mmap(addr, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON,
+	    -1, 0);
+	assert(ret != NULL);
+
+	if (ret == MAP_FAILED)
+		ret = NULL;
+	else if (addr != NULL && ret != addr) {
+		/*
+		 * We succeeded in mapping memory, but not in the right place.
+		 */
+		pages_unmap(ret, size);
+		ret = NULL;
+	}
+#endif
+	assert(ret == NULL || (addr == NULL && ret != addr)
+	    || (addr != NULL && ret == addr));
+	return (ret);
+}
+
+void
+pages_unmap(void *addr, size_t size)
+{
+
+#ifdef _WIN32
+	if (VirtualFree(addr, 0, MEM_RELEASE) == 0)
+#else
+	if (munmap(addr, size) == -1)
+#endif
+	{
+		char buf[BUFERROR_BUF];
+
+		buferror(get_errno(), buf, sizeof(buf));
+		malloc_printf("<jemalloc>: Error in "
+#ifdef _WIN32
+		              "VirtualFree"
+#else
+		              "munmap"
+#endif
+		              "(): %s\n", buf);
+		if (opt_abort)
+			abort();
+	}
+}
+
+void *
+pages_trim(void *addr, size_t alloc_size, size_t leadsize, size_t size)
+{
+	void *ret = (void *)((uintptr_t)addr + leadsize);
+
+	assert(alloc_size >= leadsize + size);
+#ifdef _WIN32
+	{
+		void *new_addr;
+
+		pages_unmap(addr, alloc_size);
+		new_addr = pages_map(ret, size);
+		if (new_addr == ret)
+			return (ret);
+		if (new_addr)
+			pages_unmap(new_addr, size);
+		return (NULL);
+	}
+#else
+	{
+		size_t trailsize = alloc_size - leadsize - size;
+
+		if (leadsize != 0)
+			pages_unmap(addr, leadsize);
+		if (trailsize != 0)
+			pages_unmap((void *)((uintptr_t)ret + size), trailsize);
+		return (ret);
+	}
+#endif
+}
+
+static bool
+pages_commit_impl(void *addr, size_t size, bool commit)
+{
+
+#ifndef _WIN32
+	if (config_debug) {
+		int prot = commit ? (PROT_READ | PROT_WRITE) : PROT_NONE;
+		void *result = mmap(addr, size, prot, MAP_PRIVATE | MAP_ANON |
+		    MAP_FIXED, -1, 0);
+		if (result == MAP_FAILED)
+			return (true);
+		if (result != addr) {
+			/*
+			 * We succeeded in mapping memory, but not in the right
+			 * place.
+			 */
+			pages_unmap(result, size);
+			return (true);
+		}
+		return (false);
+	}
+#endif
+	return (true);
+}
+
+bool
+pages_commit(void *addr, size_t size)
+{
+
+	return (pages_commit_impl(addr, size, true));
+}
+
+bool
+pages_decommit(void *addr, size_t size)
+{
+
+	return (pages_commit_impl(addr, size, false));
+}
+
+bool
+pages_purge(void *addr, size_t size)
+{
+	bool unzeroed;
+
+#ifdef _WIN32
+	VirtualAlloc(addr, size, MEM_RESET, PAGE_READWRITE);
+	unzeroed = true;
+#elif defined(JEMALLOC_HAVE_MADVISE)
+#  ifdef JEMALLOC_PURGE_MADVISE_DONTNEED
+#    define JEMALLOC_MADV_PURGE MADV_DONTNEED
+#    define JEMALLOC_MADV_ZEROS true
+#  elif defined(JEMALLOC_PURGE_MADVISE_FREE)
+#    define JEMALLOC_MADV_PURGE MADV_FREE
+#    define JEMALLOC_MADV_ZEROS false
+#  else
+#    error "No madvise(2) flag defined for purging unused dirty pages."
+#  endif
+	int err = madvise(addr, size, JEMALLOC_MADV_PURGE);
+	unzeroed = (!JEMALLOC_MADV_ZEROS || err != 0);
+#  undef JEMALLOC_MADV_PURGE
+#  undef JEMALLOC_MADV_ZEROS
+#else
+	/* Last resort no-op. */
+	unzeroed = true;
+#endif
+	return (unzeroed);
+}
+