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From: Matthew Wilcox <willy@infradead.org>
To: Marc Orr <marcorr@google.com>
Cc: kvm@vger.kernel.org, jmattson@google.com, rientjes@google.com,
	konrad.wilk@oracle.com, linux-mm@kvack.org,
	akpm@linux-foundation.org, pbonzini@redhat.com,
	rkrcmar@redhat.com, sean.j.christopherson@intel.com,
	Dave Hansen <dave.hansen@linux.intel.com>
Subject: Re: [kvm PATCH v4 0/2] use vmalloc to allocate vmx vcpus
Date: Fri, 26 Oct 2018 07:45:28 -0700	[thread overview]
Message-ID: <20181026144528.GS25444@bombadil.infradead.org> (raw)
In-Reply-To: <20181026122948.GQ25444@bombadil.infradead.org>

On Fri, Oct 26, 2018 at 05:29:48AM -0700, Matthew Wilcox wrote:
> A question that may have been asked already, but if so I didn't see it ...
> does kvm_vcpu need to be so damn big?  It's 22kB with the random .config
> I happen to have (which gets rounded to 32kB, an order-3 allocation).  If
> we can knock 6kB off it (either by allocating pieces separately), it becomes
> an order-2 allocation.  So, biggest chunks:
> 
>         struct kvm_vcpu_arch       arch;                 /*   576 21568 */
> 
>         struct kvm_mmu             mmu;                  /*   336   400 */
>         struct kvm_mmu             nested_mmu;           /*   736   400 */
>         struct fpu                 user_fpu;             /*  2176  4160 */
>         struct fpu                 guest_fpu;            /*  6336  4160 */
>         struct kvm_cpuid_entry2    cpuid_entries[80];    /* 10580  3200 */
>         struct x86_emulate_ctxt    emulate_ctxt;         /* 13792  2656 */
>         struct kvm_pmu             pmu;                  /* 17344  1520 */
>         struct kvm_vcpu_hv         hyperv;               /* 18872  1872 */
>                 gfn_t              gfns[64];             /* 20832   512 */
> 
> that's about 19kB of the 22kB right there.  Can any of them be shrunk
> in size or allocated separately?

I just had a fun conversation with Dave Hansen (cc'd) in which he
indicated that the fpu should definitely be dynamically allocated.
See also his commits from 2015 around XSAVE.

0c8c0f03e3a292e031596484275c14cf39c0ab7a
4109ca066b6b899ac7549bf3aac94b178ac95891

  reply	other threads:[~2018-10-26 14:45 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-26  7:58 [kvm PATCH v4 0/2] use vmalloc to allocate vmx vcpus Marc Orr
2018-10-26  7:58 ` [kvm PATCH v4 1/2] kvm: vmx: refactor vmx_msrs struct for vmalloc Marc Orr
2018-10-26 11:02   ` Sean Christopherson
2018-10-26  7:59 ` [kvm PATCH v4 2/2] kvm: vmx: use vmalloc() to allocate vcpus Marc Orr
2018-10-26 12:29 ` [kvm PATCH v4 0/2] use vmalloc to allocate vmx vcpus Matthew Wilcox
2018-10-26 14:45   ` Matthew Wilcox [this message]
2018-10-26 14:49     ` Dave Hansen
2018-10-31 13:06       ` Marc Orr
2018-10-29  1:58 ` Wanpeng Li
2018-10-29 16:25   ` Jim Mattson
2018-10-29 16:48     ` Matthew Wilcox
2018-10-29 18:12       ` Jim Mattson
2018-10-29 19:16         ` Marc Orr
2018-10-29 19:22           ` Marc Orr
2018-10-31 13:17       ` Marc Orr
2018-10-31 13:27         ` Matthew Wilcox
2018-10-31 13:48           ` Marc Orr
2018-10-31 14:21             ` Matthew Wilcox
2018-10-31 21:19               ` Marc Orr

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