Re: [PATCH 0/2] Reduce lock contention related with large folio

[Ryan Roberts <ryan.roberts@arm.com>]

On 17/04/2023 08:56, Yin Fengwei wrote:
> Ryan tried to enable the large folio for anonymous mapping [1].
> 
> Unlike large folio for page cache which doesn't trigger frequent page
> allocation/free, large folio for anonymous mapping is allocated/freeed
> more frequently. So large folio for anonymous mapping exposes some lock
> contention.
> 
> Ryan mentioned the deferred queue lock in [1]. We also met other two
> lock contention: lru lock and zone lock.
> 
> This series tries to mitigate the deferred queue lock and reduce lru
> lock in some level.
> 
> The patch1 tries to reduce deferred queue lock by not acquiring queue
> lock when check whether the folio is in deferred list or not. Test
> page fault1 of will-it-scale showed 60% deferred queue lock contention
> reduction.
> 
> The patch2 tries to reduce lru lock by allowing batched add large folio
> to lru list. Test page fault1 of will-it-scale showed 20% lru lock
> contention reduction.
> 
> The zone lock contention happens on large folio free path and related
> with commit f26b3fa04611 "mm/page_alloc: limit number of high-order
> pages on PCP during bulk free" and will not be address by this series.

I applied this series on top of mine and did some quick perf tests. See
https://lore.kernel.org/linux-mm/d9987135-3a8a-e22c-13f9-506d3249332b@arm.com/.
The change is certainly reducing time spent in the kernel, but there are other
problems I'll need to investigate. So:

Tested-by: Ryan Roberts <ryan.roberts@arm.com>

Thanks,
Ryan

> 
> 
> [1]
> https://lore.kernel.org/linux-mm/20230414130303.2345383-1-ryan.roberts@arm.com/
> 
> Yin Fengwei (2):
>   THP: avoid lock when check whether THP is in deferred list
>   lru: allow large batched add large folio to lru list
> 
>  include/linux/pagevec.h | 19 +++++++++++++++++--
>  mm/huge_memory.c        | 19 ++++++++++++++++---
>  mm/swap.c               |  3 +--
>  3 files changed, 34 insertions(+), 7 deletions(-)
>