RFC: [PATCH] disabling buckets under "low memory"

Maksim Yevmenkin maksim.yevmenkin at gmail.com
Wed May 23 18:05:14 UTC 2012


hello,

would anyone object to the following patch?

===

Index: uma_core.c
===================================================================
--- uma_core.c	(revision 616)
+++ uma_core.c	(working copy)
@@ -267,10 +267,7 @@
 static void
 bucket_enable(void)
 {
-	if (cnt.v_free_count < cnt.v_free_min)
-		bucketdisable = 1;
-	else
-		bucketdisable = 0;
+	bucketdisable = vm_page_count_min();
 }

===

i've observed situation where per-cpu buckets were disabled while
there were enough free cached pages. basically, cnt.v_free_count was
sitting stable at a value lower than cnt.v_free_min and that caused
massive performance drop. tuning down vm.v_free_min sysctl immediately
helped.

thanks,
max


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