Messages in this thread | | | Subject | Re: [RFC PATCH v1 00/13] lru_lock scalability | From | Steven Whitehouse <> | Date | Thu, 1 Feb 2018 15:54:38 +0000 |
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Hi,
On 31/01/18 23:04, daniel.m.jordan@oracle.com wrote: > lru_lock, a per-node* spinlock that protects an LRU list, is one of the > hottest locks in the kernel. On some workloads on large machines, it > shows up at the top of lock_stat. > > One way to improve lru_lock scalability is to introduce an array of locks, > with each lock protecting certain batches of LRU pages. > > *ooooooooooo**ooooooooooo**ooooooooooo**oooo ... > | || || || > \ batch 1 / \ batch 2 / \ batch 3 / > > In this ASCII depiction of an LRU, a page is represented with either '*' > or 'o'. An asterisk indicates a sentinel page, which is a page at the > edge of a batch. An 'o' indicates a non-sentinel page. > > To remove a non-sentinel LRU page, only one lock from the array is > required. This allows multiple threads to remove pages from different > batches simultaneously. A sentinel page requires lru_lock in addition to > a lock from the array. > > Full performance numbers appear in the last patch in this series, but this > prototype allows a microbenchmark to do up to 28% more page faults per > second with 16 or more concurrent processes. > > This work was developed in collaboration with Steve Sistare. > > Note: This is an early prototype. I'm submitting it now to support my > request to attend LSF/MM, as well as get early feedback on the idea. Any > comments appreciated. > > > * lru_lock is actually per-memcg, but without memcg's in the picture it > becomes per-node. GFS2 has an lru list for glocks, which can be contended under certain workloads. Work is still ongoing to figure out exactly why, but this looks like it might be a good approach to that issue too. The main purpose of GFS2's lru list is to allow shrinking of the glocks under memory pressure via the gfs2_scan_glock_lru() function, and it looks like this type of approach could be used there to improve the scalability,
Steve.
> > Aaron Lu (1): > mm: add a percpu_pagelist_batch sysctl interface > > Daniel Jordan (12): > mm: allow compaction to be disabled > mm: add lock array to pgdat and batch fields to struct page > mm: introduce struct lru_list_head in lruvec to hold per-LRU batch > info > mm: add batching logic to add/delete/move API's > mm: add lru_[un]lock_all APIs > mm: convert to-be-refactored lru_lock callsites to lock-all API > mm: temporarily convert lru_lock callsites to lock-all API > mm: introduce add-only version of pagevec_lru_move_fn > mm: add LRU batch lock API's > mm: use lru_batch locking in release_pages > mm: split up release_pages into non-sentinel and sentinel passes > mm: splice local lists onto the front of the LRU > > include/linux/mm_inline.h | 209 +++++++++++++++++++++++++++++++++++++++++++++- > include/linux/mm_types.h | 5 ++ > include/linux/mmzone.h | 25 +++++- > kernel/sysctl.c | 9 ++ > mm/Kconfig | 1 - > mm/huge_memory.c | 6 +- > mm/memcontrol.c | 5 +- > mm/mlock.c | 11 +-- > mm/mmzone.c | 7 +- > mm/page_alloc.c | 43 +++++++++- > mm/page_idle.c | 4 +- > mm/swap.c | 208 ++++++++++++++++++++++++++++++++++++--------- > mm/vmscan.c | 49 +++++------ > 13 files changed, 500 insertions(+), 82 deletions(-) >
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