linux-kernel - Re: [PATCH 1/1] mm: handle profiling for fake memory allocations during compaction

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Message-ID: <CAJuCfpHXOP9-Zd1aYhtXjy7hOHZ-ZFdOXyoRpGQwFvvBFxj-CA@mail.gmail.com>
Date: Tue, 2 Jul 2024 15:17:01 +0000
From: Suren Baghdasaryan <surenb@...gle.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: akpm@...ux-foundation.org, kent.overstreet@...ux.dev, 
	pasha.tatashin@...een.com, souravpanda@...gle.com, keescook@...omium.org, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] mm: handle profiling for fake memory allocations
 during compaction

On Tue, Jul 2, 2024 at 9:32 AM Vlastimil Babka <vbabka@...e.cz> wrote:
>
> On 6/30/24 9:17 PM, Suren Baghdasaryan wrote:
> > On Mon, Jun 17, 2024 at 1:33 AM Vlastimil Babka <vbabka@...e.cz> wrote:
> >>
> >> On 6/15/24 1:05 AM, Suren Baghdasaryan wrote:
> >> > During compaction isolated free pages are marked allocated so that they
> >> > can be split and/or freed. For that, post_alloc_hook() is used inside
> >> > split_map_pages() and release_free_list(). split_map_pages() marks free
> >> > pages allocated, splits the pages and then lets alloc_contig_range_noprof()
> >> > free those pages. release_free_list() marks free pages and immediately
> >>
> >> Well in case of split_map_pages() only some of them end up freed, but most
> >> should be used as migration targets. But we move the tags from the source
> >> page during migration and unaccount the ones from the target (i.e. from the
> >> instrumented post_alloc_hook() after this patch), right? So it should be ok,
> >> just the description here is incomplete.
> >
> > Sorry for the delay with replying, Vlastimil.
> > Yes, you are correct. Some of these pages are not immediately freed
> > but migrated and during migration the destination gets charged for
> > them. As a result these new counters should still read 0 most of the
> > time except for some intermediate states.
> > I can amend the description if this is considered important.
>
> The fix was merged to mainline already.

Oh, didn't realize that. Ok, will have to keep it as is then.

>