linux-kernel - Re: [PATCH] lz4: fix performance regressions

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Message-ID: <20170213133703.GC31635@1wt.eu>
Date:   Mon, 13 Feb 2017 14:37:03 +0100
From:   Willy Tarreau <w@....eu>
To:     Sven Schmidt <4sschmid@...ormatik.uni-hamburg.de>
Cc:     minchan@...nel.org, ebiggers3@...il.com, akpm@...ux-foundation.org,
        bongkyu.kim@....com, rsalvaterra@...il.com,
        sergey.senozhatsky@...il.com, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, herbert@...dor.apana.org.au,
        davem@...emloft.net, linux-crypto@...r.kernel.org,
        anton@...msg.org, ccross@...roid.com, keescook@...omium.org,
        tony.luck@...el.com
Subject: Re: [PATCH] lz4: fix performance regressions

On Mon, Feb 13, 2017 at 12:53:49PM +0100, Sven Schmidt wrote:
> On Sun, Feb 12, 2017 at 10:41:17PM +0100, Willy Tarreau wrote:
> > On Sun, Feb 12, 2017 at 04:20:00PM +0100, Sven Schmidt wrote:
> > > On Sun, Feb 12, 2017 at 02:05:08PM +0100, Willy Tarreau wrote:
> > > > Hi Sven,
> > > > 
> > > > On Sun, Feb 12, 2017 at 12:16:18PM +0100, Sven Schmidt wrote:
> > > > > Fix performance regressions compared to current kernel LZ4
> > > > 
> > > > Your patch contains mostly style cleanups which certainly are welcome
> > > > but make the whole patch hard to review. These cleanups would have been
> > > > better into a separate, preliminary patch IMHO.
> > > > 
> > > > Regards,
> > > > Willy
> > > 
> > > Hi Willy,
> > > 
> > > the problem was, I wanted to compare my version to the upstream LZ4 to find bugs (as with my last patch version: wrong indentation in LZ4HC 
> > > in two for loops). But since the LZ4 code is a pain to read, I made additional style cleanups "on the way".
> > 
> > Oh I can easily understand!
> > 
> > > Hope you can manage to review the patch though, because it is difficult to separate the cleanups now.
> > 
> > When I need to split a patch into pieces, usually what I do is that I
> > revert it, re-apply it without committing, then "git add -p", validate
> > all the hunks to be taken as the first patch (ie here the cleanups),
> > commit, then commit the rest as a separate one. It seems to me that the
> > fix is in the last few hunks though I'm not sure yet.
> > 
> > Thanks,
> > Willy
> 
> Hi Willy,
> 
> I didn't know about this 'trick' until now. Thanks for sharing it! I gave it a short try recently, that's really cool!
> 
> Since the problem discussed in this branch of this thread seems to be solved (see Minchans E-Mail), I won't split the patches, though.
> Or is there an actual need for doing so? I will send an updated patchset (containing these patches + the other ones suggested by Eric) later.

It's probably too late for this time, but keep it in mind for next time :-)

willy