lkml.org 
[lkml]   [2018]   [Dec]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v4 0/7] lib/lzo: performance improvements
From
Date
On 2018-11-30 15:26, Dave Rodgman wrote:
> This patch series introduces performance improvements for lzo.
>
> The previous version of this patchset is here:
> https://lkml.org/lkml/2018/11/30/807
>
> This version of the patchset fixes a maybe-used-uninitialized warning
> (although the previous version was still safe).
>
> Dave

Hi Dave,

as indicated in my previous mail please split your series into three
distinct pull requests.


Request 1 - ARM64 improvements; acked by me

[PATCH 1/8] lib/lzo: tidy-up ifdefs
[PATCH 3/8] lib/lzo: enable 64-bit CTZ on Arm
[PATCH 4/8] lib/lzo: 64-bit CTZ on arm64
[PATCH 5/8] lib/lzo: fast 8-byte copy on arm64

are simple arch patches that give a nice speedup on ARM64 and should
get merged ASAP.



Request 2 - add COPY16; *NOT* acked by me

[PATCH 2/8] lib/lzo: clean-up by introducing COPY16

is still not correct because of possible overlapping copies. I'll
address this on the weekend.



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

This can *NOT* be applied in the current implementation.

It (1) silently changes the compressed data format, (2) crashes on MIPS,
and (3) makes compression and decompression on typical data 10% slower on
X86_64 with our internal benchmarks, and (4) has to be carefully checked
for buffer overflows.

I understand that we want some optimizations for data with many zeros like
in the typical ZRAM use case, but the implementation will clearly need some
more work. I'll also have a look at the weekend - eg I have a nice idea
how to deal with (1).



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.

Cheers,
Markus



--
Markus Oberhumer, <markus@oberhumer.com>, http://www.oberhumer.com/

\
 
 \ /
  Last update: 2018-12-06 16:48    [W:0.147 / U:9.668 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site