svn commit: r348117 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs

[Alexander Motin]

Author: mav
Date: Wed May 22 18:43:48 2019
New Revision: 348117
URL: https://svnweb.freebsd.org/changeset/base/348117

Log:
  Allocate buffers smaller then ABD chunk size as linear.
  
  This allows to reduce memory waste by letting UMA to put multiple small
  buffers into one memory page slab.  The page sharing means that UMA
  may not be able to free memory page when some of buffers are freed, but
  alternatively memory used by that buffer would just be wasted from the
  beginning.
  
  This change follows alike change in ZoL, but unlike Linux (according to
  my understanding of it from comments) FreeBSD never shares slabs bigger
  then one memory page, so this should be even less invasive then there.
  
  MFC after:	2 weeks
  Sponsored by:	iXsystems, Inc.

Modified:
  head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/abd.c

Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/abd.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/abd.c	Wed May 22 17:42:22 2019	(r348116)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/abd.c	Wed May 22 18:43:48 2019	(r348117)
@@ -290,7 +290,7 @@ abd_free_struct(abd_t *abd)
 abd_t *
 abd_alloc(size_t size, boolean_t is_metadata)
 {
-	if (!zfs_abd_scatter_enabled)
+	if (!zfs_abd_scatter_enabled || size <= zfs_abd_chunk_size)
 		return (abd_alloc_linear(size, is_metadata));
 
 	VERIFY3U(size, <=, SPA_MAXBLOCKSIZE);