Sample and cache RSS in serverCron().

Obtaining the RSS (Resident Set Size) info is slow in Linux and OSX.
This slowed down the generation of the INFO 'memory' section.

Since the RSS does not require to be a real-time measurement, we
now sample it with server.hz frequency (10 times per second by default)
and use this value both to show the INFO rss field and to compute the
fragmentation ratio.

Practically this does not make any difference for memory profiling of
Redis but speeds up the INFO call significantly.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/zmalloc.h b/src/zmalloc.h
index 331d8e433..72a4f8138 100644
--- a/src/zmalloc.h
+++ b/src/zmalloc.h
@@ -73,7 +73,7 @@ char *zstrdup(const char *s);
 size_t zmalloc_used_memory(void);
 void zmalloc_enable_thread_safeness(void);
 void zmalloc_set_oom_handler(void (*oom_handler)(size_t));
-float zmalloc_get_fragmentation_ratio(void);
+float zmalloc_get_fragmentation_ratio(size_t rss);
 size_t zmalloc_get_rss(void);
 size_t zmalloc_get_private_dirty(void);
 void zlibc_free(void *ptr);