diff --git a/doc/bird.sgml b/doc/bird.sgml
index 5e48e342..f84aef26 100644
--- a/doc/bird.sgml
+++ b/doc/bird.sgml
@@ -722,6 +722,37 @@ include "tablename.conf";;
 	Evaluates given filter expression. It is used by the developers for testing of filters.
 </descrip>
 
+<sect>Global performance options
+<label id="perf-opts">
+
+<p>The internal scheduler and allocator can be tweaked if needed. You probably
+don't want to do this, yet if you encounter some weird performance problem,
+these knobs may be handy. For now, all the options are concentrated in the
+<cf/memory {}/ block.
+
+<descrip>
+	<tag><label id="memory-global-keep-hot">global keep hot <m/number/</tag>
+	How much memory is kept hot at most in the global memory storage.
+	Overflowing memory is returned back to the OS. The virtual memory,
+        aka address space, is kept in the cold storage and may be later reused,
+        to prevent address space fragmentation problems.
+	Aligned automatically to the system page size.
+	This knob must be higher than the following memory settings.
+	Default: 16777216.
+
+	<tag><label id="memory-local-keep-hot">local keep hot <m/number/</tag>
+	How much memory is kept hot at most in every thread-local memory storage.
+	Overflowing memory is moved to the global hot storage.
+	Aligned automatically to the system page size.
+	This knob must be higher than the following memory settings.
+	Default: 524288.
+
+	<tag><label id="memory-local-keep-hot">allocate block <m/number/</tag>
+	How much memory is allocated at once when no more memory is neither
+	in available hot nor cold storages.
+	Aligned automatically to the system page size.
+	Default: 131072.
+</descrip>
 
 <sect>Routing table options
 <label id="rtable-opts">
diff --git a/lib/resource.h b/lib/resource.h
index 2d540723..b980b669 100644
--- a/lib/resource.h
+++ b/lib/resource.h
@@ -146,16 +146,19 @@ void buffer_realloc(void **buf, unsigned *size, unsigned need, unsigned item_siz
 /* Allocator of whole pages; for use in slabs and other high-level allocators. */
 #define PAGE_HEAD(x)	((void *) (((uintptr_t) (x)) & ~(page_size-1)))
 extern long page_size;
-extern _Atomic int pages_kept;
-extern _Atomic int pages_kept_locally;
-extern _Atomic int pages_kept_cold;
-extern _Atomic int pages_kept_cold_index;
+extern _Atomic uint pages_kept;
+extern _Atomic uint pages_kept_locally;
+extern _Atomic uint pages_kept_cold;
+extern _Atomic uint pages_kept_cold_index;
 void *alloc_page(void);
 void free_page(void *);
 void flush_local_pages(void);
 
 void resource_sys_init(void);
 
+struct alloc_config;
+void alloc_preconfig(struct alloc_config *);
+
 #ifdef HAVE_LIBDMALLOC
 /*
  * The standard dmalloc macros tend to produce lots of namespace
diff --git a/lib/runtime.h b/lib/runtime.h
index 450eb26a..877b46ac 100644
--- a/lib/runtime.h
+++ b/lib/runtime.h
@@ -24,6 +24,12 @@ enum latency_debug_flags {
   DL_TIMERS = 0x40,
 };
 
+struct alloc_config {
+  uint keep_mem_max_global;		/* How much free memory is kept hot in total */
+  uint keep_mem_max_local;		/* How much free memory is kept hot in every thread */
+  uint at_once;				/* How much memory to allocate at once */
+};
+
 #define GLOBAL_RUNTIME_CONTENTS \
   struct timeformat tf_log;		/* Time format for the logfile */		\
   struct timeformat tf_base;		/* Time format for other purposes */		\
@@ -32,6 +38,7 @@ enum latency_debug_flags {
   u32 latency_limit;			/* Events with longer duration are logged (us) */	\
   u32 watchdog_warning;			/* I/O loop watchdog limit for warning (us) */	\
   const char *hostname;			/* Hostname */					\
+  struct alloc_config alloc;		/* Allocation settings */			\
 
 struct global_runtime { GLOBAL_RUNTIME_CONTENTS };
 extern struct global_runtime * _Atomic global_runtime;
diff --git a/sysdep/unix/alloc.c b/sysdep/unix/alloc.c
index 0432b9e2..28905418 100644
--- a/sysdep/unix/alloc.c
+++ b/sysdep/unix/alloc.c
@@ -32,13 +32,19 @@
 long page_size = 0;
 
 #ifdef HAVE_MMAP
-# define KEEP_PAGES_MAX	16384
-# define KEEP_PAGES_MIN	32
-# define KEEP_PAGES_MAX_LOCAL	128
-# define ALLOC_PAGES_AT_ONCE	32
 
-  STATIC_ASSERT(KEEP_PAGES_MIN * 4 < KEEP_PAGES_MAX);
-  STATIC_ASSERT(ALLOC_PAGES_AT_ONCE < KEEP_PAGES_MAX_LOCAL);
+void
+alloc_preconfig(struct alloc_config *ac)
+{
+  ac->keep_mem_max_global = 16777216;
+  ac->keep_mem_max_local = 524288;
+  ac->at_once = 131072;
+}
+
+# define ALLOC_INFO (&(atomic_load_explicit(&global_runtime, memory_order_relaxed)->alloc))
+# define KEEP_MEM_MAX		ALLOC_INFO->keep_mem_max_global
+# define KEEP_MEM_MAX_LOCAL	ALLOC_INFO->keep_mem_max_local
+# define ALLOC_MEM_AT_ONCE	ALLOC_INFO->at_once
 
   static bool use_fake = 0;
   static bool initialized = 0;
@@ -124,8 +130,8 @@ long page_size = 0;
 
   static DOMAIN(resource) empty_pages_domain;
   static struct empty_pages *empty_pages = NULL;
-  _Atomic int pages_kept_cold = 0;
-  _Atomic int pages_kept_cold_index = 0;
+  _Atomic uint pages_kept_cold = 0;
+  _Atomic uint pages_kept_cold_index = 0;
 
   static struct free_page * _Atomic page_stack = NULL;
   static _Thread_local struct free_page * local_page_stack = NULL;
@@ -143,14 +149,14 @@ long page_size = 0;
   static event page_cleanup_event = { .hook = page_cleanup, };
 # define SCHEDULE_CLEANUP  do if (initialized && !shutting_down) ev_send(&global_event_list, &page_cleanup_event); while (0)
 
-  _Atomic int pages_kept = 0;
-  _Atomic int pages_kept_locally = 0;
-  static _Thread_local int pages_kept_here = 0;
+  _Atomic uint pages_kept = 0;
+  _Atomic uint pages_kept_locally = 0;
+  static _Thread_local uint pages_kept_here = 0;
 
   static void *
   alloc_sys_page(void)
   {
-    void *ptr = mmap(NULL, page_size * ALLOC_PAGES_AT_ONCE, PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+    void *ptr = mmap(NULL, ALLOC_MEM_AT_ONCE, PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 
     if (ptr == MAP_FAILED)
       die("mmap(%ld) failed: %m", (s64) page_size);
@@ -258,8 +264,8 @@ alloc_page(void)
   void *ptr = alloc_sys_page();
   ajlog(ptr, NULL, 0, AJT_ALLOC_MMAP);
 
-  for (int i=1; i<ALLOC_PAGES_AT_ONCE; i++)
-    free_page(ptr + page_size * i);
+  for (unsigned long skip = page_size; skip<ALLOC_MEM_AT_ONCE; skip += page_size)
+    free_page(ptr + skip);
 
   return ptr;
 #endif
@@ -278,7 +284,7 @@ free_page(void *ptr)
 #ifdef HAVE_MMAP
   /* We primarily try to keep the pages locally. */
   struct free_page *fp = ptr;
-  if (pages_kept_here < KEEP_PAGES_MAX_LOCAL)
+  if (pages_kept_here * page_size < KEEP_MEM_MAX_LOCAL)
   {
     struct free_page *next = local_page_stack;
     atomic_store_explicit(&fp->next, next, memory_order_relaxed);
@@ -304,7 +310,7 @@ free_page(void *ptr)
   ajlog(fp, next, pk, AJT_FREE_GLOBAL_HOT);
 
   /* And if there are too many global hot free pages, we ask for page cleanup */
-  if (pk >= KEEP_PAGES_MAX)
+  if (pk * page_size >= KEEP_MEM_MAX)
     SCHEDULE_CLEANUP;
 #endif
 }
@@ -322,7 +328,7 @@ flush_local_pages(void)
   /* We first count the pages to enable consistency checking.
    * Also, we need to know the last page. */
   struct free_page *last = local_page_stack, *next;
-  int check_count = 1;
+  uint check_count = 1;
   while (next = atomic_load_explicit(&last->next, memory_order_relaxed))
   {
     check_count++;
@@ -348,7 +354,7 @@ flush_local_pages(void)
 
   /* Check the state of global page cache and maybe schedule its cleanup. */
   atomic_fetch_sub_explicit(&pages_kept_locally, check_count, memory_order_relaxed);
-  if (atomic_fetch_add_explicit(&pages_kept, check_count, memory_order_relaxed) >= KEEP_PAGES_MAX)
+  if (atomic_fetch_add_explicit(&pages_kept, check_count, memory_order_relaxed) * page_size >= KEEP_MEM_MAX)
     SCHEDULE_CLEANUP;
 }
 
@@ -362,7 +368,7 @@ page_cleanup(void *_ UNUSED)
 
   /* Pages allocated inbetween */
   uint pk = atomic_load_explicit(&pages_kept, memory_order_relaxed);
-  if (pk < KEEP_PAGES_MAX)
+  if (pk * page_size < KEEP_MEM_MAX)
     return;
 
   /* Walk the pages */
@@ -420,7 +426,7 @@ page_cleanup(void *_ UNUSED)
     UNLOCK_DOMAIN(resource, empty_pages_domain);
     count++;
   }
-  while (atomic_fetch_sub_explicit(&pages_kept, 1, memory_order_relaxed) >= KEEP_PAGES_MAX / 2);
+  while (atomic_fetch_sub_explicit(&pages_kept, 1, memory_order_relaxed) * page_size >= KEEP_MEM_MAX / 2);
 
   ALLOC_TRACE("Moved %u pages to cold storage, now %u cold, %u index", count,
       atomic_load_explicit(&pages_kept_cold, memory_order_relaxed),
@@ -450,9 +456,12 @@ resource_sys_init(void)
     /* We assume that page size has only one bit and is between 1K and 256K (incl.).
      * Otherwise, the assumptions in lib/slab.c (sl_head's num_full range) aren't met. */
 
+    alloc_preconfig(&(atomic_load_explicit(&global_runtime, memory_order_relaxed)->alloc));
+
     empty_pages_domain = DOMAIN_NEW(resource);
     DOMAIN_SETUP(resource, empty_pages_domain, "Empty Pages", NULL);
     initialized = 1;
+
     return;
   }
 
@@ -462,5 +471,7 @@ resource_sys_init(void)
 #endif
 
   page_size = 4096;
+  alloc_preconfig(&(atomic_load_explicit(&global_runtime, memory_order_relaxed)->alloc));
+
   initialized = 1;
 }
diff --git a/sysdep/unix/config.Y b/sysdep/unix/config.Y
index c00c2377..3f7bb59a 100644
--- a/sysdep/unix/config.Y
+++ b/sysdep/unix/config.Y
@@ -21,6 +21,7 @@ CF_KEYWORDS(LOG, SYSLOG, ALL, DEBUG, TRACE, INFO, REMOTE, WARNING, ERROR, AUTH,
 CF_KEYWORDS(NAME, CONFIRM, UNDO, CHECK, TIMEOUT, DEBUG, LATENCY, LIMIT, WATCHDOG, WARNING, STATUS)
 CF_KEYWORDS(PING, WAKEUP, SOCKETS, SCHEDULING, EVENTS, TIMERS, ALLOCATOR)
 CF_KEYWORDS(GRACEFUL, RESTART, FIXED)
+CF_KEYWORDS(MEMORY, GLOBAL, LOCAL, KEEP, HOT, ALLOCATE, BLOCK)
 
 %type <i> log_mask log_mask_list log_cat cfg_timeout debug_unix latency_debug_mask latency_debug_flag latency_debug_list
 %type <t> cfg_name
@@ -156,6 +157,28 @@ latency_debug_flag:
  | TIMERS	{ $$ = DL_TIMERS; }
  ;
 
+conf: MEMORY '{' memory_items '}'
+{
+  if (new_config->runtime.alloc.keep_mem_max_global <= new_config->runtime.alloc.keep_mem_max_local)
+    cf_error("Global (%u) hot memory limit must be higher than local (%u)",
+	new_config->runtime.alloc.keep_mem_max_global,
+	new_config->runtime.alloc.keep_mem_max_local);
+
+  if (new_config->runtime.alloc.keep_mem_max_local < new_config->runtime.alloc.at_once)
+    cf_error("Can't allocate more memory at once (%u) than local hot limit (%u)",
+	new_config->runtime.alloc.at_once,
+	new_config->runtime.alloc.keep_mem_max_local);
+}
+
+memory_items:
+ | memory_items GLOBAL KEEP HOT NUM ';' {
+   new_config->runtime.alloc.keep_mem_max_global = BIRD_ALIGN($5, page_size); }
+ | memory_items LOCAL KEEP HOT NUM ';' {
+   new_config->runtime.alloc.keep_mem_max_local = BIRD_ALIGN($5, page_size); }
+ | memory_items ALLOCATE BLOCK NUM ';' {
+   new_config->runtime.alloc.at_once = BIRD_ALIGN($4, page_size); }
+;
+
 
 /* Unix specific commands */
 
diff --git a/sysdep/unix/main.c b/sysdep/unix/main.c
index 6385fb06..081f29b8 100644
--- a/sysdep/unix/main.c
+++ b/sysdep/unix/main.c
@@ -194,6 +194,8 @@ sysdep_preconfig(struct config *c)
   c->runtime.latency_limit = UNIX_DEFAULT_LATENCY_LIMIT;
   c->runtime.watchdog_warning = UNIX_DEFAULT_WATCHDOG_WARNING;
 
+  alloc_preconfig(&c->runtime.alloc);
+
 #ifdef PATH_IPROUTE_DIR
   read_iproute_table(c, PATH_IPROUTE_DIR "/rt_protos", "ipp_", 255);
   read_iproute_table(c, PATH_IPROUTE_DIR "/rt_realms", "ipr_", 0xffffffff);
diff --git a/test/birdtest.c b/test/birdtest.c
index b5ea4cb0..f63718a0 100644
--- a/test/birdtest.c
+++ b/test/birdtest.c
@@ -557,7 +557,9 @@ void cmd_reconfig_undo_notify(void) {}
 #include "nest/bird.h"
 #include "lib/net.h"
 #include "conf/conf.h"
-void sysdep_preconfig(struct config *c UNUSED) {}
+void sysdep_preconfig(struct config *c) {
+  alloc_preconfig(&c->runtime.alloc);
+}
 
 void bird_thread_commit(struct thread_config *new);
 void sysdep_commit(struct config *new, struct config *old UNUSED)