From: "H. Peter Anvin" <hpa@zytor.com>
To: "Luck, Tony" <tony.luck@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"x86@kernel.org" <x86@kernel.org>,
Josh Poimboeuf <jpoimboe@kernel.org>,
"Lutomirski, Andy" <luto@kernel.org>,
Jonathan Corbet <corbet@lwn.net>, "Christopherson,,
Sean" <seanjc@google.com>, Paolo Bonzini <pbonzini@redhat.com>,
"ak@linux.intel.com" <ak@linux.intel.com>,
"tim.c.chen@linux.intel.com" <tim.c.chen@linux.intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
Alyssa Milburn <alyssa.milburn@linux.intel.com>,
Daniel Sneddon <daniel.sneddon@linux.intel.com>,
"antonio.gomez.iglesias@linux.intel.com"
<antonio.gomez.iglesias@linux.intel.com>,
"Milburn, Alyssa" <alyssa.milburn@intel.com>
Subject: RE: [PATCH v2 1/6] x86/bugs: Add asm helpers for executing VERW
Date: Tue, 24 Oct 2023 13:30:04 -0700 [thread overview]
Message-ID: <49A97ACF-24A3-452C-88A5-0D55F77B7780@zytor.com> (raw)
In-Reply-To: <SJ1PR11MB6083FE98A35C6BCF027B568CFCDFA@SJ1PR11MB6083.namprd11.prod.outlook.com>
On October 24, 2023 12:40:02 PM PDT, "Luck, Tony" <tony.luck@intel.com> wrote:
>> Sure it could, but it would mean the kernel is sitting on an average of 6 MB of unusable memory. It would also mean that unloaded modules would create holes in that memory which would have to be managed.
>
>On my Fedora38 desktop:
>
>$ lsmod | awk '{ bytes += $2 } END {print bytes/(1024*1024)}'
>21.0859
>
>Lots more than 6MB memory already essentially pinned by loaded modules.
>
>$ head -3 /proc/meminfo
>MemTotal: 65507344 kB
>MemFree: 56762336 kB
>MemAvailable: 63358552 kB
>
>Pinning 20 or so Mbytes isn't going to make a dent in that free memory.
>
>Managing the holes for unloading/reloading modules adds some complexity ... but shouldn't be awful.
>
>If this code managed at finer granularity than "page", it would save some memory.
>
>$ lsmod | wc -l
>123
>
>All those modules rounding text/data up to 4K boundaries is wasting a bunch of it.
>
>-Tony
>
>
>
Sure, but is it worth the effort?
next prev parent reply other threads:[~2023-10-24 20:30 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-24 8:08 [PATCH v2 0/6] Delay VERW Pawan Gupta
2023-10-24 8:08 ` [PATCH v2 1/6] x86/bugs: Add asm helpers for executing VERW Pawan Gupta
2023-10-24 10:36 ` Peter Zijlstra
2023-10-24 16:35 ` Pawan Gupta
2023-10-24 16:36 ` Peter Zijlstra
2023-10-24 16:45 ` Pawan Gupta
2023-10-24 17:02 ` Peter Zijlstra
2023-10-24 17:30 ` Pawan Gupta
2023-10-24 18:27 ` H. Peter Anvin
2023-10-24 18:49 ` Luck, Tony
2023-10-24 19:14 ` H. Peter Anvin
2023-10-24 19:40 ` Luck, Tony
2023-10-24 20:30 ` H. Peter Anvin [this message]
2023-10-24 22:30 ` Peter Zijlstra
2023-10-24 22:28 ` Peter Zijlstra
2023-10-25 4:00 ` Pawan Gupta
2023-10-25 6:56 ` Peter Zijlstra
2023-10-25 15:06 ` Pawan Gupta
2023-10-25 6:58 ` Peter Zijlstra
2023-10-25 15:10 ` Pawan Gupta
2023-10-24 8:08 ` [PATCH v2 2/6] x86/entry_64: Add VERW just before userspace transition Pawan Gupta
2023-10-24 8:08 ` [PATCH v2 3/6] x86/entry_32: " Pawan Gupta
2023-10-24 8:08 ` [PATCH v2 4/6] x86/bugs: Use ALTERNATIVE() instead of mds_user_clear static key Pawan Gupta
2023-10-25 22:08 ` kernel test robot
2023-10-24 8:08 ` [PATCH v2 5/6] KVM: VMX: Use BT+JNC, i.e. EFLAGS.CF to select VMRESUME vs. VMLAUNCH Pawan Gupta
2023-10-25 8:15 ` Nikolay Borisov
2023-10-24 8:08 ` [PATCH v2 6/6] KVM: VMX: Move VERW closer to VMentry for MDS mitigation Pawan Gupta
2023-10-25 7:47 ` Chao Gao
2023-10-25 15:15 ` Pawan Gupta
2023-10-24 12:26 ` [PATCH v2 0/6] Delay VERW Matthew Wilcox
2023-10-24 17:01 ` Pawan Gupta
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