From: Dave Rodgman <dave.rodgman@arm.com>
To: "Markus F.X.J. Oberhumer" <markus@oberhumer.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>
Cc: "herbert@gondor.apana.org.au" <herbert@gondor.apana.org.au>,
"davem@davemloft.net" <davem@davemloft.net>,
Matt Sealey <Matt.Sealey@arm.com>,
"nitingupta910@gmail.com" <nitingupta910@gmail.com>,
"minchan@kernel.org" <minchan@kernel.org>,
"sergey.senozhatsky.work@gmail.com"
<sergey.senozhatsky.work@gmail.com>,
"sonnyrao@google.com" <sonnyrao@google.com>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
nd <nd@arm.com>, "sfr@canb.auug.org.au" <sfr@canb.auug.org.au>
Subject: Re: [PATCH v4 0/7] lib/lzo: performance improvements
Date: Mon, 7 Jan 2019 15:35:55 +0000 [thread overview]
Message-ID: <a545e3a2-6d68-e0ba-7d98-168d3637858a@arm.com> (raw)
In-Reply-To: <fba24452-ae3a-0caa-11b4-aea69abf2fff@arm.com>
Hi Markus,
What are your thoughts on how we should proceed with this patchset? You raised a few concerns in December - however, I'm
not sure what further changes might be needed, if any. IMO this could be merged as it stands.
Regarding compatibility concerns: patchset v4 does not modify the behaviour of existing lzo. It introduces an
independent algorithm (closely based on lzo); and also introduces some Arm performance benefits for existing lzo,
without modifying the behaviour. So I don't see a compatibility risk.
You mentioned a crash on MIPS - do you have any details on this please? I have not seen any crashes in my testing so I'm
not able to look into this without more data.
On 07/12/2018 3:54 pm, Dave Rodgman wrote:
> Hi Markus,
>
> On 06/12/2018 3:47 pm, Markus F.X.J. Oberhumer wrote:> Request 3 - add lzo-rle; *NOT* acked by me
> >
> > [PATCH 6/8] lib/lzo: implement run-length encoding
> > [PATCH 7/8] lib/lzo: separate lzo-rle from lzo
> > [PATCH 8/8] zram: default to lzo-rle instead of lzo
> >
> > It (1) silently changes the compressed data format
>
> I'm not sure this is relevant: as a separate algorithm, there's no reason
> to retain the same format (although backwards compatibility can help with
> migration). If you know of a way to improve the compatibility aspect
> though, that would be great!
>
> > (2) crashes on MIPS,
>
> Please could you provide more detail? I tested on x86-32, x86-64, arm,
> arm64 and big-endian MIPS64, but if there is an issue I missed I'd like to
> address it.
>
> > and (3) makes compression and decompression on typical data 10% slower on
> > X86_64 with our internal benchmarks,
>
> It is of course data-dependent. In my testing, as I mentioned previously, RLE
> without the other patches does regress slightly on high-entropy data, but
> offers a win on low-entropy data. For the right applications (e.g., zram),
> this makes it overall beneficial.
>
> > and (4) has to be carefully checked for buffer overflows.
>
> This has been reviewed prior to sharing on LKML, and of course tested,
> but further review is of course welcome.
>
> > As a final comment, I question the quality your benchmarks - combining
> > arch-related ARM64 improvements and algorithmic changes into one
> > benchmark comparision is just unprofessional marketing.
>
> I felt it was helpful to show overall performance with the complete patchset:
> this is what end-users experience. However, as you can see below, I also
> previously shared a summary of the two main components of the patchset to
> try and address this sort of concern:
>
> >> As a quick summary of the impact of these patches on bigger chunks of
> >> data, I've compared the performance of four different variants of lzo
> >> on two large (~40 MB) files. The numbers show round-trip throughput
> >> in MB/s:
> >>
> >> Variant | Low-entropy | High-entropy
> >> Current lzo | 242 | 157
> >> Arm opts | 290 | 159
> >> RLE | 876 | 151
> >> Arm opts + RLE | 1150 | 181
Regards
Dave
prev parent reply other threads:[~2019-01-07 15:36 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-30 14:26 [PATCH v4 0/7] lib/lzo: performance improvements Dave Rodgman
2018-11-30 14:26 ` [PATCH 1/8] lib/lzo: tidy-up ifdefs Dave Rodgman
2018-12-06 15:49 ` Markus F.X.J. Oberhumer
2018-11-30 14:26 ` [PATCH 2/8] lib/lzo: clean-up by introducing COPY16 Dave Rodgman
2018-12-06 15:56 ` Markus F.X.J. Oberhumer
2018-11-30 14:26 ` [PATCH 3/8] lib/lzo: enable 64-bit CTZ on Arm Dave Rodgman
2018-12-06 15:51 ` Markus F.X.J. Oberhumer
2018-11-30 14:26 ` [PATCH 4/8] lib/lzo: 64-bit CTZ on arm64 Dave Rodgman
2018-12-06 15:52 ` Markus F.X.J. Oberhumer
2018-11-30 14:26 ` [PATCH 5/8] lib/lzo: fast 8-byte copy " Dave Rodgman
2018-12-06 15:53 ` Markus F.X.J. Oberhumer
2018-11-30 14:26 ` [PATCH 6/8] lib/lzo: implement run-length encoding Dave Rodgman
2018-12-06 15:56 ` Markus F.X.J. Oberhumer
2018-11-30 14:26 ` [PATCH 7/8] lib/lzo: separate lzo-rle from lzo Dave Rodgman
2018-12-01 8:48 ` Herbert Xu
2018-11-30 14:26 ` [PATCH 8/8] zram: default to lzo-rle instead of lzo Dave Rodgman
2018-12-05 7:30 ` [PATCH v4 0/7] lib/lzo: performance improvements Sergey Senozhatsky
2018-12-05 9:50 ` Dave Rodgman
2018-12-05 10:20 ` Sergey Senozhatsky
2018-12-06 15:47 ` Markus F.X.J. Oberhumer
2018-12-06 16:22 ` Matt Sealey
2018-12-07 15:54 ` Dave Rodgman
2019-01-07 15:35 ` Dave Rodgman [this message]
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