linux-kernel - Re: [PATCH v2 0/5] Fix the incorrect memmep defer init handling and do some cleanup

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Date:   Wed, 23 Dec 2020 10:05:34 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        gopakumarr@...are.com, rppt@...nel.org, david@...hat.com
Subject: Re: [PATCH v2 0/5] Fix the incorrect memmep defer init handling and
 do some cleanup

On 12/22/20 at 05:46pm, Andrew Morton wrote:
> On Sun, 20 Dec 2020 16:27:49 +0800 Baoquan He <bhe@...hat.com> wrote:
> 
> > VMware reported the performance regression during memmap_init() invocation.
> > And they bisected to commit 73a6e474cb376 ("mm: memmap_init: iterate over
> > memblock regions rather that check each PFN") causing it.
> > 
> > https://lore.kernel.org/linux-mm/DM6PR05MB52921FF90FA01CC337DD23A1A4080@DM6PR05MB5292.namprd05.prod.outlook.com/
> > 
> > After investigation, it's caused by incorrect memmap init defer handling
> > in memmap_init_zone() after commit 73a6e474cb376. The current
> > memmap_init_zone() only handle one memory region of one zone, while
> > memmap_init() iterates over all its memory regions and pass them one by
> > one into memmap_init_zone() to handle.
> > 
> > So in this patchset, patch 1/5 fixes the bug observed by VMware. Patch
> > 2~5/5 clean up codes.
> > accordingly.
> 
> This series doesn't apply well to current mainline (plus, perhaps,
> material which I sent to Linus today).
> 
> So please check all that against mainline in a day or so, refresh,
> retest and resend.
> 
> Please separate the fix for the performance regression (1/5) into a
> single standalone patch, ready for -stable backporting.  And then a
> separate 4-patch series with the cleanups for a 5.11 merge.

Sure, doing now. 

By the way, when sending patches to linux-mm ML, which branch should I
rebase them on? I usually take your akpm/master as base, thought this
will make your patch picking easier. Seems my understanding is not true,
akpm/master is changed very soon, we should always base patch on linus's
master branch, whether patch is sending to linux-mm or not, right?

Thanks
Baoquan