Return -1 for generic kmem cache shrinker

It has been observed that it's possible to get in a state where shrink_slabs() will spin repeated invoking the generic kmem cache shrinker. It fails to detect it's not making forward progress reclaiming from the cache and doesn't give up. To ensure this never occurs we unconditionally return -1 after reclaiming what we can. Signed-off-by: Brian Behlendorf <[email protected]> Signed-off-by: Richard Yao <[email protected]> Closes openzfs/zfs#1276 Closes openzfs/zfs#1598 Closes openzfs/zfs#1432
openzfs · Jul 30, 2013 · b9b3715 · b9b3715
1 parent c47efbc
commit b9b3715
Showing 1 changed file with 9 additions and 1 deletion.
diff --git a/module/spl/spl-kmem.c b/module/spl/spl-kmem.c
@@ -2122,7 +2122,15 @@ __spl_kmem_cache_generic_shrinker(struct shrinker *shrink,
 	}
 	up_read(&spl_kmem_cache_sem);
 
-	return (unused * sysctl_vfs_cache_pressure) / 100;
+	/*
+	 * After performing reclaim always return -1 to indicate we cannot
+	 * perform additional reclaim.  This prevents shrink_slabs() from
+	 * repeatedly invoking this generic shrinker and potentially spinning.
+	 */
+	if (sc->nr_to_scan)
+		return -1;
+
+	return unused;
 }
 
 SPL_SHRINKER_CALLBACK_WRAPPER(spl_kmem_cache_generic_shrinker);