linux-kernel - Re: [PATCH v3 31/35] lib: add memory allocations report in show

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <6mjunla45lkwqvkq7jegiw5lfmufg4y53zegevep3iwvy77xub@2nfmbeo6tvz2>
Date: Thu, 15 Feb 2024 18:54:25 -0500
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Steven Rostedt <rostedt@...dmis.org>, Vlastimil Babka <vbabka@...e.cz>, 
	Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>, akpm@...ux-foundation.org, 
	hannes@...xchg.org, roman.gushchin@...ux.dev, mgorman@...e.de, dave@...olabs.net, 
	willy@...radead.org, liam.howlett@...cle.com, corbet@....net, void@...ifault.com, 
	peterz@...radead.org, juri.lelli@...hat.com, catalin.marinas@....com, will@...nel.org, 
	arnd@...db.de, tglx@...utronix.de, mingo@...hat.com, 
	dave.hansen@...ux.intel.com, x86@...nel.org, peterx@...hat.com, david@...hat.com, 
	axboe@...nel.dk, mcgrof@...nel.org, masahiroy@...nel.org, nathan@...nel.org, 
	dennis@...nel.org, tj@...nel.org, muchun.song@...ux.dev, rppt@...nel.org, 
	paulmck@...nel.org, pasha.tatashin@...een.com, yosryahmed@...gle.com, 
	yuzhao@...gle.com, dhowells@...hat.com, hughd@...gle.com, andreyknvl@...il.com, 
	keescook@...omium.org, ndesaulniers@...gle.com, vvvvvv@...gle.com, 
	gregkh@...uxfoundation.org, ebiggers@...gle.com, ytcoode@...il.com, 
	vincent.guittot@...aro.org, dietmar.eggemann@....com, bsegall@...gle.com, bristot@...hat.com, 
	vschneid@...hat.com, cl@...ux.com, penberg@...nel.org, iamjoonsoo.kim@....com, 
	42.hyeyoo@...il.com, glider@...gle.com, elver@...gle.com, dvyukov@...gle.com, 
	shakeelb@...gle.com, songmuchun@...edance.com, jbaron@...mai.com, rientjes@...gle.com, 
	minchan@...gle.com, kaleshsingh@...gle.com, kernel-team@...roid.com, 
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, iommu@...ts.linux.dev, 
	linux-arch@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-mm@...ck.org, 
	linux-modules@...r.kernel.org, kasan-dev@...glegroups.com, cgroups@...r.kernel.org
Subject: Re: [PATCH v3 31/35] lib: add memory allocations report in show_mem()

On Thu, Feb 15, 2024 at 03:19:33PM -0800, Dave Hansen wrote:
> On 2/15/24 15:07, Steven Rostedt wrote:
> > Just adding the patches increases the size by 5k. But the rest shows an
> > increase of 259k, and you are worried about 4k (and possibly less?)???
> 
> Doesn't the new page_ext thingy add a pointer per 'struct page', or
> ~0.2% of RAM, or ~32MB on a 16GB laptop?  I, too, am confused why 4k is
> even remotely an issue.

page_ext adds a separate per-page array; it itself does not add a
pointer to strugt page, it's an array lookup that uses the page pfn.

We do add a pointer to page_ext, and that's (for now) unavoidable
overhead - but we'll be looking at referencing code tags by index, and
if that works out we'll be able to kill the page_ext dependency and just
store the alloc tag index in page bits.