linux-kernel - RE: [PATCH v3 11/13] mm: zswap: Allocate acomp_batch_ctx resources for a given zswap

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Message-ID: <SJ0PR11MB5678221143E2B0A7FADFDAFFC95C2@SJ0PR11MB5678.namprd11.prod.outlook.com>
Date: Thu, 7 Nov 2024 22:22:11 +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"
	<yosryahmed@...gle.com>, "nphamcs@...il.com" <nphamcs@...il.com>,
	"chengming.zhou@...ux.dev" <chengming.zhou@...ux.dev>,
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	<ryan.roberts@....com>, "Huang, Ying" <ying.huang@...el.com>,
	"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 11/13] mm: zswap: Allocate acomp_batch_ctx resources
 for a given zswap_pool.


> -----Original Message-----
> From: Johannes Weiner <hannes@...xchg.org>
> Sent: Thursday, November 7, 2024 9:31 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 11/13] mm: zswap: Allocate acomp_batch_ctx
> resources for a given zswap_pool.
> 
> On Wed, Nov 06, 2024 at 11:21:03AM -0800, Kanchana P Sridhar wrote:
> > If the zswap_pool is associated with an acomp_alg/crypto_acomp that has
> > registered batch_compress() and batch_decompress() API, we can allocate
> the
> > necessary batching resources for the pool's acomp_batch_ctx.
> >
> > This patch makes the above determination on incurring the per-cpu memory
> > footprint cost for batching, and if so, goes ahead and allocates
> > SWAP_CRYPTO_BATCH_SIZE (i.e. 8) acomp_reqs/buffers for the
> > pool->acomp_batch_ctx on that specific cpu.
> >
> > It also "remembers" the pool's batching readiness as a result of the above,
> > through a new
> >
> >    	enum batch_comp_status can_batch_comp;
> >
> > member added to struct zswap_pool, for fast retrieval during
> > zswap_store().
> >
> > This allows us a way to only incur the memory footprint cost of the
> > pool->acomp_batch_ctx resources for a given cpu on which zswap_store()
> > needs to process a large folio.
> >
> > Suggested-by: Yosry Ahmed <yosryahmed@...gle.com>
> > Suggested-by: Ying Huang <ying.huang@...el.com>
> > Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@...el.com>
> 
> A general observation: this is a lot of code for a hardware specific
> feature that many CPUs and architectures do not support. Please keep
> the code self-contained, and wrap struct members and functions in a
> new CONFIG option, so that not everybody has to compile this in.

Thanks for this suggestion! Sure, I will address this in v4.

Thanks,
Kanchana