From: Jan Kiszka <jan.kiszka@web.de>
To: Avi Kivity <avi@redhat.com>
Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org
Subject: Re: [PATCH] memory: synchronize dirty bitmap before unmapping a range
Date: Mon, 01 Aug 2011 09:52:26 +0200 [thread overview]
Message-ID: <4E365B3A.7050701@web.de> (raw)
In-Reply-To: <4E365718.2060500@web.de>
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On 2011-08-01 09:34, Jan Kiszka wrote:
> On 2011-07-31 21:47, Avi Kivity wrote:
>> When a range is being unmapped, ask accelerators (e.g. kvm) to synchronize the
>> dirty bitmap to avoid losing information forever.
>>
>> Fixes grub2 screen update.
>
> I does.
>
> But something is still broken. As I reported before, the performance of
> grub2 startup is an order of magnitude slower than with the existing
> code. According to ftrace, we are getting tons of additional
> EPT_MISCONFIG exits over the 0xA0000 segment. But I haven't spot the
> difference yet. The effective slot setup as communicated to kvm looks
> innocent.
I take it back: We obviously once in a while resume the guest with the
vga segment unmapped. And that, of course, ends up doing mmio instead of
plain ram accesses.
Jan
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WARNING: multiple messages have this Message-ID (diff)
From: Jan Kiszka <jan.kiszka@web.de>
To: Avi Kivity <avi@redhat.com>
Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org
Subject: Re: [Qemu-devel] [PATCH] memory: synchronize dirty bitmap before unmapping a range
Date: Mon, 01 Aug 2011 09:52:26 +0200 [thread overview]
Message-ID: <4E365B3A.7050701@web.de> (raw)
In-Reply-To: <4E365718.2060500@web.de>
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On 2011-08-01 09:34, Jan Kiszka wrote:
> On 2011-07-31 21:47, Avi Kivity wrote:
>> When a range is being unmapped, ask accelerators (e.g. kvm) to synchronize the
>> dirty bitmap to avoid losing information forever.
>>
>> Fixes grub2 screen update.
>
> I does.
>
> But something is still broken. As I reported before, the performance of
> grub2 startup is an order of magnitude slower than with the existing
> code. According to ftrace, we are getting tons of additional
> EPT_MISCONFIG exits over the 0xA0000 segment. But I haven't spot the
> difference yet. The effective slot setup as communicated to kvm looks
> innocent.
I take it back: We obviously once in a while resume the guest with the
vga segment unmapped. And that, of course, ends up doing mmio instead of
plain ram accesses.
Jan
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next prev parent reply other threads:[~2011-08-01 7:52 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-31 19:47 [PATCH] memory: synchronize dirty bitmap before unmapping a range Avi Kivity
2011-07-31 19:47 ` [Qemu-devel] " Avi Kivity
2011-08-01 7:34 ` Jan Kiszka
2011-08-01 7:34 ` [Qemu-devel] " Jan Kiszka
2011-08-01 7:52 ` Jan Kiszka [this message]
2011-08-01 7:52 ` Jan Kiszka
2011-08-01 8:16 ` Avi Kivity
2011-08-01 8:16 ` [Qemu-devel] " Avi Kivity
2011-08-01 9:05 ` Jan Kiszka
2011-08-01 9:05 ` [Qemu-devel] " Jan Kiszka
2011-08-01 9:30 ` Avi Kivity
2011-08-01 9:30 ` [Qemu-devel] " Avi Kivity
2011-08-01 9:32 ` Avi Kivity
2011-08-01 9:32 ` [Qemu-devel] " Avi Kivity
2011-08-01 9:45 ` Avi Kivity
2011-08-01 9:45 ` [Qemu-devel] " Avi Kivity
2011-08-01 10:21 ` Jan Kiszka
2011-08-01 10:21 ` [Qemu-devel] " Jan Kiszka
2011-08-01 10:27 ` Avi Kivity
2011-08-01 10:27 ` [Qemu-devel] " Avi Kivity
2011-08-05 16:47 ` Anthony Liguori
2011-08-05 16:47 ` Anthony Liguori
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