Re: [RFC PATCH v1 13/13] mm: vmscan, swap, zswap: Compress batching of folios in shrink_folio_list().

[Joel Granados <joel.granados@kernel.org>]

On Thu, Oct 17, 2024 at 11:41:01PM -0700, Kanchana P Sridhar wrote:
> This patch enables the use of Intel IAA hardware compression acceleration
> to reclaim a batch of folios in shrink_folio_list(). This results in
> reclaim throughput and workload/sys performance improvements.
> 
> The earlier patches on compress batching deployed multiple IAA compress
> engines for compressing up to SWAP_CRYPTO_SUB_BATCH_SIZE pages within a
> large folio that is being stored in zswap_store(). This patch further
> propagates the efficiency improvements demonstrated with IAA "batching
> within folios", to vmscan "batching of folios" which will also use
> batching within folios using the extensible architecture of
> the __zswap_store_batch_core() procedure added earlier, that accepts
> an array of folios.

...

> +static inline void zswap_store_batch(struct swap_in_memory_cache_cb *simc)
> +{
> +}
> +
>  static inline bool zswap_store(struct folio *folio)
>  {
>  	return false;
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 79e6cb1d5c48..b8d6b599e9ae 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -2064,6 +2064,15 @@ static struct ctl_table vm_table[] = {
>  		.extra1		= SYSCTL_ZERO,
>  		.extra2		= (void *)&page_cluster_max,
>  	},
> +	{
> +		.procname	= "compress-batchsize",
> +		.data		= &compress_batchsize,
> +		.maxlen		= sizeof(int),
> +		.mode		= 0644,
> +		.proc_handler	= proc_dointvec_minmax,
Why not use proc_douintvec_minmax? These are the reasons I think you
should use that (please correct me if I miss-read your patch):

1. Your range is [1,32] -> so no negative values
2. You are using the value to compare with an unsinged int
   (simc->nr_folios) in your `struct swap_in_memory_cache_cb`. So
   instead of going from int to uint, you should just do uint all
   around. No?
3. Using proc_douintvec_minmax will automatically error out on negative
   input without event considering your range, so there is less code
   executed at the end.

> +		.extra1		= SYSCTL_ONE,
> +		.extra2		= (void *)&compress_batchsize_max,
> +	},
>  	{
>  		.procname	= "dirtytime_expire_seconds",
>  		.data		= &dirtytime_expire_interval,
> diff --git a/mm/page_io.c b/mm/page_io.c
> index a28d28b6b3ce..065db25309b8 100644
> --- a/mm/page_io.c
> +++ b/mm/page_io.c
> @@ -226,6 +226,131 @@ static void swap_zeromap_folio_clear(struct folio *folio)
>  	}
>  }

...

Best

-- 

Joel Granados