linux-kernel - Re: [RFC 00/14] Dynamic Kernel Stacks

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: <mo2z7sfzxntlfbbr5yqyjpe5cn2nn6ecxgi3pr5kcfbzq2dnzn@vvtugr3s5hbf>
Date: Thu, 14 Mar 2024 15:28:58 -0400
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Pasha Tatashin <pasha.tatashin@...een.com>
Cc: "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org, akpm@...ux-foundation.org, x86@...nel.org, bp@...en8.de, 
	brauner@...nel.org, bristot@...hat.com, bsegall@...gle.com, 
	dave.hansen@...ux.intel.com, dianders@...omium.org, dietmar.eggemann@....com, 
	eric.devolder@...cle.com, hca@...ux.ibm.com, hch@...radead.org, 
	jacob.jun.pan@...ux.intel.com, jgg@...pe.ca, jpoimboe@...nel.org, jroedel@...e.de, 
	juri.lelli@...hat.com, kinseyho@...gle.com, kirill.shutemov@...ux.intel.com, 
	lstoakes@...il.com, luto@...nel.org, mgorman@...e.de, mic@...ikod.net, 
	michael.christie@...cle.com, mingo@...hat.com, mjguzik@...il.com, mst@...hat.com, 
	npiggin@...il.com, peterz@...radead.org, pmladek@...e.com, 
	rick.p.edgecombe@...el.com, rostedt@...dmis.org, surenb@...gle.com, tglx@...utronix.de, 
	urezki@...il.com, vincent.guittot@...aro.org, vschneid@...hat.com
Subject: Re: [RFC 00/14] Dynamic Kernel Stacks

On Thu, Mar 14, 2024 at 03:23:08PM -0400, Pasha Tatashin wrote:
> > >
> > > My point is that what matters is total memory use, not just memory used in
> > > the kernel. Amdahl's law.
> >
> > If userspace is running a few processes with many threads and the
> > userspace stacks are small, kernel stacks could end up dominating.
> >
> > I'd like to see some numbers though.
> 
> The unused kernel stack pages occupy petabytes of memory across the fleet [1].

Raw number doesn't mean much here (I know how many machines Google has,
of course it's going to be petabytes ;), percentage of system memory
would be better.

What I'd _really_ like to see is raw output from memory allocation
profiling, so we can see how much memory is going to kernel stacks vs.
other kernel allocations.

Number of kernel threads vs. number of user threads would also be good
to know - I've been seeing ps output lately where we've got a lot more
workqueue workers than we should, perhaps that's something that could be
addressed.