Messages in this thread | | | From | Martin Steigerwald <> | Subject | zswap: How to determine whether it is compressing swap pages? | Date | Wed, 17 Jul 2013 12:04:38 +0200 |
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Hi Seth, hi everyone,
Yesterday I build 3.11-rc1 with CONFIG_ZSWAP and wanted to test it.
I added zswap.enabled=1 and get:
martin@merkaba:~> dmesg | grep zswap [ 0.000000] Command line: BOOT_IMAGE=/vmlinuz-3.11.0-rc1-tp520+ root=/dev/mapper/merkaba-debian ro rootflags=subvol=root init=/bin/systemd cgroup_enable=memory threadirqs i915.i915_enable_rc6=7 zcache zswap.enabled=1 [ 0.000000] Kernel command line: BOOT_IMAGE=/vmlinuz-3.11.0-rc1-tp520+ root=/dev/mapper/merkaba-debian ro rootflags=subvol=root init=/bin/systemd cgroup_enable=memory threadirqs i915.i915_enable_rc6=7 zcache zswap.enabled=1 [ 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 order to allocate some swap.
Still I think zswap didn´t 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=4 destroy_by_rcu:0 grep: free_calls: Die angeforderte Funktion ist nicht implementiert hwcache_align:0 min_partial:5 objects:2550 N0=2550 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=30 slabs_cpu_partial:0(0) slab_size:48 store_user:0 total_objects:2550 N0=2550 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 compresses swap device pages on the block device level in addition to compressing read cache pages of usual filesystems. Which one takes precedence, zcache or zswap? Can I disable zcache for swap device?
Here is dmesg for zcache:
martin@merkaba:~> dmesg | grep zcache [ 0.000000] Command line: BOOT_IMAGE=/vmlinuz-3.11.0-rc1-tp520+ root=/dev/mapper/merkaba-debian ro rootflags=subvol=root init=/bin/systemd cgroup_enable=memory threadirqs i915.i915_enable_rc6=7 zcache zswap.enabled=1 [ 0.000000] Kernel command line: BOOT_IMAGE=/vmlinuz-3.11.0-rc1-tp520+ root=/dev/mapper/merkaba-debian ro rootflags=subvol=root init=/bin/systemd cgroup_enable=memory threadirqs i915.i915_enable_rc6=7 zcache zswap.enabled=1 [ 1.453531] zcache: using lzo compressor [ 1.453634] zcache: cleancache enabled using kernel transcendent memory and compression buddies [ 1.453679] zcache: frontswap enabled using kernel transcendent memory and compression buddies [ 1.453722] zcache: frontswap_ops overridden [ 5.358288] zcache: created ephemeral local tmem pool, id=0 [ 8.155684] zcache: created persistent local tmem pool, id=1 [ 8.331680] zcache: created ephemeral local tmem pool, id=2 [ 8.593235] zcache: created ephemeral local tmem pool, id=3 [ 8.743330] zcache: created ephemeral local tmem pool, id=4
Thanks, -- Martin 'Helios' Steigerwald - http://www.Lichtvoll.de GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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