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Debabrata Banerjee
44813aefad
Calling it when nothing is evictable will cause extra kswapd cpu. Also if we didn't shrink it's unlikely to have memory to reap because we likely just called it microseconds ago. The exception is if we are in direct reclaim. You can see how hard this is being hit in kswapd with a light test workload: 34.95% [zfs] [k] arc_kmem_reap_now 5.40% [spl] [k] spl_kmem_cache_reap_now 3.79% [kernel] [k] _raw_spin_lock 2.86% [spl] [k] __spl_kmem_cache_generic_shrinker.isra.7 2.70% [kernel] [k] shrink_slab.part.37 1.93% [kernel] [k] isolate_lru_pages.isra.43 1.55% [kernel] [k] __wake_up_bit 1.20% [kernel] [k] super_cache_count 1.20% [kernel] [k] __radix_tree_lookup With ZFS just mounted but only ext4/pagecache memory pressure arc_kmem_reap_now still consumes excessive CPU: 12.69% [kernel] [k] isolate_lru_pages.isra.43 10.76% [kernel] [k] free_pcppages_bulk 7.98% [kernel] [k] drop_buffers 7.31% [kernel] [k] shrink_page_list 6.44% [zfs] [k] arc_kmem_reap_now 4.19% [kernel] [k] free_hot_cold_page 4.00% [kernel] [k] __slab_free 3.95% [kernel] [k] __isolate_lru_page 3.09% [kernel] [k] __radix_tree_lookup Same pagecache only workload as above with this patch series: 11.58% [kernel] [k] isolate_lru_pages.isra.43 11.20% [kernel] [k] drop_buffers 9.67% [kernel] [k] free_pcppages_bulk 8.44% [kernel] [k] shrink_page_list 4.86% [kernel] [k] __isolate_lru_page 4.43% [kernel] [k] free_hot_cold_page 4.00% [kernel] [k] __slab_free 3.44% [kernel] [k] __radix_tree_lookup (arc_kmem_reap_now has 0 samples in perf) AKAMAI: zfs: CR 3695042 Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed-by: Richard Yao <ryao@gentoo.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Debabrata Banerjee <dbanerje@akamai.com> Issue #6035
ZFS on Linux, which is also known as ZoL, is currently feature complete. It includes fully functional and stable SPA, DMU, ZVOL, and ZPL layers. And it's native!
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