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

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Message-ID: <20201223081210.GC2205@MiWiFi-R3L-srv>
Date:   Wed, 23 Dec 2020 16:12:10 +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 12/23/20 at 10:05am, Baoquan He wrote:
> 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.

Have sent the 1/5 as a standalone patch. Will send the rest 4 patches as
a patchset once the patch 1/5 is merged into linux-next. Thanks, Andrew.

> 
> 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?