RE: [PATCH v13 22/22] mm: zswap: Batched zswap_compress() with compress batching of large folios.

[Sridhar, Kanchana P]

> -----Original Message-----
> From: Yosry Ahmed <yosry.ahmed@xxxxxxxxx>
> Sent: Thursday, November 13, 2025 4:46 PM
> To: Sridhar, Kanchana P <kanchana.p.sridhar@xxxxxxxxx>
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> Subject: Re: [PATCH v13 22/22] mm: zswap: Batched zswap_compress() with
> compress batching of large folios.
[...]
> > > > Architectural considerations for the zswap batching framework:
> > > >
> > >
> ==============================================================
> > > > We have designed the zswap batching framework to be
> > > > hardware-agnostic. It has no dependencies on Intel-specific features
> and
> > > > can be leveraged by any hardware accelerator or software-based
> > > > compressor. In other words, the framework is open and inclusive by
> > > > design.
> > > >
> > > > Other ongoing work that can use batching:
> > > > =========================================
> > > > This patch-series demonstrates the performance benefits of compress
> > > > batching when used in zswap_store() of large folios. shrink_folio_list()
> > > > "reclaim batching" of any-order folios is the major next work that uses
> > > > the zswap compress batching framework: our testing of
> kernel_compilation
> > > > with writeback and the zswap shrinker indicates 10X fewer pages get
> > > > written back when we reclaim 32 folios as a batch, as compared to one
> > > > folio at a time: this is with deflate-iaa and with zstd. We expect to
> > > > submit a patch-series with this data and the resulting performance
> > > > improvements shortly. Reclaim batching relieves memory pressure
> faster
> > > > than reclaiming one folio at a time, hence alleviates the need to scan
> > > > slab memory for writeback.
> > > >
> > > > Nhat has given ideas on using batching with the ongoing kcompressd
> work,
> > > > as well as beneficially using decompression batching & block IO batching
> > > > to improve zswap writeback efficiency.
> > > >
> > > > Experiments that combine zswap compress batching, reclaim batching,
> > > > swapin_readahead() decompression batching of prefetched pages, and
> > > > writeback batching show that 0 pages are written back with deflate-iaa
> > > > and zstd. For comparison, the baselines for these compressors see
> > > > 200K-800K pages written to disk (kernel compilation 'allmod' config).
> > > >
> > > > To summarize, these are future clients of the batching framework:
> > > >
> > > >    - shrink_folio_list() reclaim batching of multiple folios:
> > > >        Implemented, will submit patch-series.
> > > >    - zswap writeback with decompress batching:
> > > >        Implemented, will submit patch-series.
> > > >    - zram:
> > > >        Implemented, will submit patch-series.
> > > >    - kcompressd:
> > > >        Not yet implemented.
> > > >    - file systems:
> > > >        Not yet implemented.
> > > >    - swapin_readahead() decompression batching of prefetched pages:
> > > >        Implemented, will submit patch-series.
> > > >
> > > > Additionally, any place we have folios that need to be compressed, can
> > > > potentially be parallelized.

[...]

> For example, you should remove mentions of ongoing work and future work,
> simply because things change and they may not land. Just briefly
> mentioning that there are future use cases (with maybe an example) is
> sufficient.

Hi Yosry,

The mentions of ongoing/future work were included as per Andrew's suggestion.
Hence, I would like to keep these in the commit log. Hope this is Ok with you?

Thanks,
Kanchana