linux-kernel - RE: [PATCH v3 12/13] mm: Add sysctl vm.compress-batching switch for compress batching during swapout.

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Message-ID: <SJ0PR11MB56785626DD03165F04F995A9C95C2@SJ0PR11MB5678.namprd11.prod.outlook.com>
Date: Thu, 7 Nov 2024 22:24:57 +0000
From: "Sridhar, Kanchana P" <kanchana.p.sridhar@...el.com>
To: Johannes Weiner <hannes@...xchg.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, "yosryahmed@...gle.com"
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	"21cnbao@...il.com" <21cnbao@...il.com>, "akpm@...ux-foundation.org"
	<akpm@...ux-foundation.org>, "linux-crypto@...r.kernel.org"
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	"Feghali, Wajdi K" <wajdi.k.feghali@...el.com>, "Gopal, Vinodh"
	<vinodh.gopal@...el.com>, "Sridhar, Kanchana P"
	<kanchana.p.sridhar@...el.com>
Subject: RE: [PATCH v3 12/13] mm: Add sysctl vm.compress-batching switch for
 compress batching during swapout.


> -----Original Message-----
> From: Johannes Weiner <hannes@...xchg.org>
> Sent: Thursday, November 7, 2024 9:34 AM
> To: Sridhar, Kanchana P <kanchana.p.sridhar@...el.com>
> Cc: linux-kernel@...r.kernel.org; linux-mm@...ck.org;
> yosryahmed@...gle.com; nphamcs@...il.com;
> chengming.zhou@...ux.dev; usamaarif642@...il.com;
> ryan.roberts@....com; Huang, Ying <ying.huang@...el.com>;
> 21cnbao@...il.com; akpm@...ux-foundation.org; linux-
> crypto@...r.kernel.org; herbert@...dor.apana.org.au;
> davem@...emloft.net; clabbe@...libre.com; ardb@...nel.org;
> ebiggers@...gle.com; surenb@...gle.com; Accardi, Kristen C
> <kristen.c.accardi@...el.com>; zanussi@...nel.org; Feghali, Wajdi K
> <wajdi.k.feghali@...el.com>; Gopal, Vinodh <vinodh.gopal@...el.com>
> Subject: Re: [PATCH v3 12/13] mm: Add sysctl vm.compress-batching switch
> for compress batching during swapout.
> 
> On Wed, Nov 06, 2024 at 11:21:04AM -0800, Kanchana P Sridhar wrote:
> > The sysctl vm.compress-batching parameter is 0 by default. If the platform
> > has Intel IAA, the user can run experiments with IAA compress batching of
> > large folios in zswap_store() as follows:
> >
> > sysctl vm.compress-batching=1
> > echo deflate-iaa > /sys/module/zswap/parameters/compressor
> 
> A sysctl seems uncalled for. Can't the batching code be gated on
> deflate-iaa being the compressor? It can still be generalized later if
> another compressor is shown to benefit from batching.

That's a very valid point. I will gate the batching code based on the
availability of the crypto batch_compress() and batch_decompress()
interfaces in the compressor. I agree, this can still be generalized later to
other compressors, potentially via these same batching API.

Thanks,
Kanchana