s390/mem_detect: replace tprot loop with binary search

In a situation when other memory detection methods are not available
(no SCLP and no z/VM diag260), continuous online memory is assumed.
Replacing tprot loop with faster binary search, as only online memory
end has to be found.

Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Reviewed-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/boot/mem_detect.c b/arch/s390/boot/mem_detect.c
index 3becf6b..65ae3c9 100644 (file)
--- a/arch/s390/boot/mem_detect.c
+++ b/arch/s390/boot/mem_detect.c
@@ -3,12 +3,10 @@
 #include <asm/sclp.h>
 #include <asm/sections.h>
 #include <asm/mem_detect.h>
+#include <asm/sparsemem.h>
 #include "compressed/decompressor.h"
 #include "boot.h"
 
-#define CHUNK_READ_WRITE 0
-#define CHUNK_READ_ONLY  1
-
 unsigned long __bootdata(max_physmem_end);
 struct mem_detect_info __bootdata(mem_detect);
 
@@ -141,38 +139,25 @@ static int tprot(unsigned long addr)
        return rc;
 }
 
-static void scan_memory(unsigned long rzm)
+static void search_mem_end(void)
 {
-       unsigned long addr, size;
-       int type;
-
-       if (!rzm)
-               rzm = 1UL << 20;
-
-       addr = 0;
-       do {
-               size = 0;
-               /* assume lowcore is writable */
-               type = addr ? tprot(addr) : CHUNK_READ_WRITE;
-               do {
-                       size += rzm;
-                       if (max_physmem_end && addr + size >= max_physmem_end)
-                               break;
-               } while (type == tprot(addr + size));
-               if (type == CHUNK_READ_WRITE || type == CHUNK_READ_ONLY) {
-                       if (max_physmem_end && (addr + size > max_physmem_end))
-                               size = max_physmem_end - addr;
-                       add_mem_detect_block(addr, addr + size);
-               }
-               addr += size;
-       } while (addr < max_physmem_end);
+       unsigned long range = 1 << (MAX_PHYSMEM_BITS - 20); /* in 1MB blocks */
+       unsigned long offset = 0;
+       unsigned long pivot;
+
+       while (range > 1) {
+               range >>= 1;
+               pivot = offset + range;
+               if (!tprot(pivot << 20))
+                       offset = pivot;
+       }
+
+       add_mem_detect_block(0, (offset + 1) << 20);
 }
 
 void detect_memory(void)
 {
-       unsigned long rzm;
-
-       sclp_early_get_meminfo(&max_physmem_end, &rzm);
+       sclp_early_get_memsize(&max_physmem_end);
 
        if (!sclp_early_read_storage_info()) {
                mem_detect.info_source = MEM_DETECT_SCLP_STOR_INFO;
@@ -190,7 +175,7 @@ void detect_memory(void)
                return;
        }
 
-       scan_memory(rzm);
-       mem_detect.info_source = MEM_DETECT_TPROT_LOOP;
+       search_mem_end();
+       mem_detect.info_source = MEM_DETECT_BIN_SEARCH;
        max_physmem_end = get_mem_detect_end();
 }

diff --git a/arch/s390/include/asm/mem_detect.h b/arch/s390/include/asm/mem_detect.h
index 153c354..6114b92 100644 (file)
--- a/arch/s390/include/asm/mem_detect.h
+++ b/arch/s390/include/asm/mem_detect.h
@@ -9,7 +9,7 @@ enum mem_info_source {
        MEM_DETECT_SCLP_STOR_INFO,
        MEM_DETECT_DIAG260,
        MEM_DETECT_SCLP_READ_INFO,
-       MEM_DETECT_TPROT_LOOP
+       MEM_DETECT_BIN_SEARCH
 };
 
 struct mem_detect_block {

diff --git a/arch/s390/include/asm/sclp.h b/arch/s390/include/asm/sclp.h
index e0da13c..32b683f 100644 (file)
--- a/arch/s390/include/asm/sclp.h
+++ b/arch/s390/include/asm/sclp.h
@@ -114,7 +114,7 @@ void sclp_early_printk(const char *s);
 void sclp_early_printk_force(const char *s);
 void __sclp_early_printk(const char *s, unsigned int len, unsigned int force);
 
-int sclp_early_get_meminfo(unsigned long *mem, unsigned long *rzm);
+int sclp_early_get_memsize(unsigned long *mem);
 int _sclp_get_core_info(struct sclp_core_info *info);
 int sclp_core_configure(u8 core);
 int sclp_core_deconfigure(u8 core);

diff --git a/drivers/s390/char/sclp_early_core.c b/drivers/s390/char/sclp_early_core.c
index 0df08dc..acfe093 100644 (file)
--- a/drivers/s390/char/sclp_early_core.c
+++ b/drivers/s390/char/sclp_early_core.c
@@ -272,7 +272,7 @@ int __init sclp_early_get_info(struct read_info_sccb *info)
        return 0;
 }
 
-int __init sclp_early_get_meminfo(unsigned long *mem, unsigned long *rzm)
+int __init sclp_early_get_memsize(unsigned long *mem)
 {
        unsigned long rnmax;
        unsigned long rnsize;
@@ -285,7 +285,6 @@ int __init sclp_early_get_meminfo(unsigned long *mem, unsigned long *rzm)
        rnsize = sccb->rnsize ? sccb->rnsize : sccb->rnsize2;
        rnsize <<= 20;
        *mem = rnsize * rnmax;
-       *rzm = rnsize;
        return 0;
 }