From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx102.postini.com [74.125.245.102]) by kanga.kvack.org (Postfix) with SMTP id 83FE46B0032 for ; Wed, 17 Jul 2013 06:04:44 -0400 (EDT) From: Martin Steigerwald Subject: zswap: How to determine whether it is compressing swap pages? Date: Wed, 17 Jul 2013 12:04:38 +0200 Message-ID: <1674223.HVFdAhB7u5@merkaba> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="iso-8859-1" Sender: owner-linux-mm@kvack.org List-ID: To: Seth Jennings , linux-mm@kvack.org, linux-kernel@vger.kernel.org Hi Seth, hi everyone, Yesterday I build 3.11-rc1 with CONFIG_ZSWAP and wanted to test it. I added zswap.enabled=3D1 and get: martin@merkaba:~> dmesg | grep zswap [ 0.000000] Command line: BOOT_IMAGE=3D/vmlinuz-3.11.0-rc1-tp520+=20= root=3D/dev/mapper/merkaba-debian ro rootflags=3Dsubvol=3Droot init=3D/= bin/systemd=20 cgroup_enable=3Dmemory threadirqs i915.i915_enable_rc6=3D7 zcache zswap= .enabled=3D1 [ 0.000000] Kernel command line: BOOT_IMAGE=3D/vmlinuz-3.11.0-rc1-tp= 520+=20 root=3D/dev/mapper/merkaba-debian ro rootflags=3Dsubvol=3Droot init=3D/= bin/systemd=20 cgroup_enable=3Dmemory threadirqs i915.i915_enable_rc6=3D7 zcache zswap= .enabled=3D1 [ 1.452443] zswap: loading zswap [ 1.452465] zswap: using lzo compressor I did a stress -m 1 --vm-keep --vm-bytes 4G on this 8 GB ThinkPad T520 = in=20 order to allocate some swap. Still I think zswap didn=B4t do anything: merkaba:/sys/kernel/debug/zswap> grep . * duplicate_entry:0 pool_limit_hit:0 pool_pages:0 reject_alloc_fail:0 reject_compress_poor:0 reject_kmemcache_fail:0 reject_reclaim_fail:0 stored_pages:0 written_back_pages:0 However: merkaba:/sys/kernel/slab/zswap_entry> grep . * aliases:9 align:8 grep: alloc_calls: Die angeforderte Funktion ist nicht implementiert cache_dma:0 cpu_partial:0 cpu_slabs:4 N0=3D4 destroy_by_rcu:0 grep: free_calls: Die angeforderte Funktion ist nicht implementiert hwcache_align:0 min_partial:5 objects:2550 N0=3D2550 object_size:48 objects_partial:0 objs_per_slab:85 order:0 partial:0 poison:0 reclaim_account:0 red_zone:0 remote_node_defrag_ratio:100 reserved:0 sanity_checks:0 slabs:30 N0=3D30 slabs_cpu_partial:0(0) slab_size:48 store_user:0 total_objects:2550 N0=3D2550 trace:0 It has some objects it seems. How do I know whether zswap actually does something? Will zswap work even with zcache enabled? As I understand zcache compre= sses=20 swap device pages on the block device level in addition to compressing = read=20 cache pages of usual filesystems. Which one takes precedence, zcache or= zswap?=20 Can I disable zcache for swap device? Here is dmesg for zcache: martin@merkaba:~> dmesg | grep zcache [ 0.000000] Command line: BOOT_IMAGE=3D/vmlinuz-3.11.0-rc1-tp520+=20= root=3D/dev/mapper/merkaba-debian ro rootflags=3Dsubvol=3Droot init=3D/= bin/systemd=20 cgroup_enable=3Dmemory threadirqs i915.i915_enable_rc6=3D7 zcache zswap= .enabled=3D1 [ 0.000000] Kernel command line: BOOT_IMAGE=3D/vmlinuz-3.11.0-rc1-tp= 520+=20 root=3D/dev/mapper/merkaba-debian ro rootflags=3Dsubvol=3Droot init=3D/= bin/systemd=20 cgroup_enable=3Dmemory threadirqs i915.i915_enable_rc6=3D7 zcache zswap= .enabled=3D1 [ 1.453531] zcache: using lzo compressor [ 1.453634] zcache: cleancache enabled using kernel transcendent mem= ory and=20 compression buddies [ 1.453679] zcache: frontswap enabled using kernel transcendent memo= ry and=20 compression buddies [ 1.453722] zcache: frontswap_ops overridden [ 5.358288] zcache: created ephemeral local tmem pool, id=3D0 [ 8.155684] zcache: created persistent local tmem pool, id=3D1 [ 8.331680] zcache: created ephemeral local tmem pool, id=3D2 [ 8.593235] zcache: created ephemeral local tmem pool, id=3D3 [ 8.743330] zcache: created ephemeral local tmem pool, id=3D4 Thanks, --=20 Martin 'Helios' Steigerwald - http://www.Lichtvoll.de GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org