linux-kernel - RE: [PATCH v1 2/2] mm: zswap: zswap_store_pages() simplifications for batching.

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Message-ID: <SJ0PR11MB5678F859FC683F09FF8EC958C9362@SJ0PR11MB5678.namprd11.prod.outlook.com>
Date: Tue, 3 Dec 2024 01:15:42 +0000
From: "Sridhar, Kanchana P" <kanchana.p.sridhar@...el.com>
To: Nhat Pham <nphamcs@...il.com>, Chengming Zhou <chengming.zhou@...ux.dev>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, "hannes@...xchg.org"
	<hannes@...xchg.org>, "yosryahmed@...gle.com" <yosryahmed@...gle.com>,
	"usamaarif642@...il.com" <usamaarif642@...il.com>, "ryan.roberts@....com"
	<ryan.roberts@....com>, "21cnbao@...il.com" <21cnbao@...il.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>, "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 v1 2/2] mm: zswap: zswap_store_pages() simplifications for
 batching.


> -----Original Message-----
> From: Nhat Pham <nphamcs@...il.com>
> Sent: Monday, December 2, 2024 4:17 PM
> To: Chengming Zhou <chengming.zhou@...ux.dev>
> Cc: Sridhar, Kanchana P <kanchana.p.sridhar@...el.com>; linux-
> kernel@...r.kernel.org; linux-mm@...ck.org; hannes@...xchg.org;
> yosryahmed@...gle.com; usamaarif642@...il.com;
> ryan.roberts@....com; 21cnbao@...il.com; akpm@...ux-foundation.org;
> Feghali, Wajdi K <wajdi.k.feghali@...el.com>; Gopal, Vinodh
> <vinodh.gopal@...el.com>
> Subject: Re: [PATCH v1 2/2] mm: zswap: zswap_store_pages() simplifications
> for batching.
> 
> On Wed, Nov 27, 2024 at 11:00 PM Chengming Zhou
> <chengming.zhou@...ux.dev> wrote:
> >
> > How about introducing a `zswap_compress_folio()` interface which
> > can be used by `zswap_store()`?
> > ```
> > zswap_store()
> >         nr_pages = folio_nr_pages(folio)
> >
> >         entries = zswap_alloc_entries(nr_pages)
> >
> >         ret = zswap_compress_folio(folio, entries, pool)
> >
> >         // store entries into xarray and LRU list
> > ```
> >
> > And this version `zswap_compress_folio()` is very simple for now:
> > ```
> > zswap_compress_folio()
> >         nr_pages = folio_nr_pages(folio)
> >
> >         for (index = 0; index < nr_pages; ++index) {
> >                 struct page *page = folio_page(folio, index);
> >
> >                 if (!zswap_compress(page, &entries[index], pool))
> >                         return false;
> >         }
> >
> >         return true;
> > ```
> > This can be easily extended to support your "batched" version.
> >
> > Then the old `zswap_store_page()` could be removed.
> >
> > The good point is simplicity, that we don't need to slice folio
> > into multiple batches, then repeat the common operations for each
> > batch, like preparing entries, storing into xarray and LRU list...
> >
> 
> +1.

Thanks Nhat. I replied with some potential considerations in my reply
to Chengming's and Yosry's comments. Would appreciate it if you can
add follow-up suggestions to that reply.

Thanks,
Kanchana