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: <20240215192141.03421b85@gandalf.local.home>
Date: Thu, 15 Feb 2024 19:21:41 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Kent Overstreet <kent.overstreet@...ux.dev>
Cc: 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, 15 Feb 2024 18:51:41 -0500
Kent Overstreet <kent.overstreet@...ux.dev> wrote:

> Most of that is data (505024), not text (68582, or 66k).
> 

And the 4K extra would have been data too.

> The data is mostly the alloc tags themselves (one per allocation
> callsite, and you compiled the entire kernel), so that's expected.
> 
> Of the text, a lot of that is going to be slowpath stuff - module load
> and unload hooks, formatt and printing the output, other assorted bits.
> 
> Then there's Allocation and deallocating obj extensions vectors - not
> slowpath but not super fast path, not every allocation.
> 
> The fastpath instruction count overhead is pretty small
>  - actually doing the accounting - the core of slub.c, page_alloc.c,
>    percpu.c
>  - setting/restoring the alloc tag: this is overhead we add to every
>    allocation callsite, so it's the most relevant - but it's just a few
>    instructions.
> 
> So that's the breakdown. Definitely not zero overhead, but that fixed
> memory overhead (and additionally, the percpu counters) is the price we
> pay for very low runtime CPU overhead.

But where are the benchmarks that are not micro-benchmarks. How much
overhead does this cause to those? Is it in the noise, or is it noticeable?

-- Steve