From: Markus Armbruster <armbru@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Lieven <pl@kamp.de>,
kwolf@redhat.com, peter.maydell@linaro.org, mst@redhat.com,
qemu-devel@nongnu.org, mreitz@redhat.com, kraxel@redhat.com,
dgilbert@redhat.com
Subject: Re: [Qemu-devel] [PATCH 07/15] qapi: use mmap for QmpInputVisitor
Date: Mon, 04 Jul 2016 13:18:03 +0200 [thread overview]
Message-ID: <87vb0llkic.fsf@dusky.pond.sub.org> (raw)
In-Reply-To: <5e0cdb47-1446-e575-a1c7-c437ac7b8e41@redhat.com> (Paolo Bonzini's message of "Mon, 4 Jul 2016 11:02:48 +0200")
Paolo Bonzini <pbonzini@redhat.com> writes:
> On 30/06/2016 16:12, Markus Armbruster wrote:
>> Implementing a stack as "big enough" array can be wasteful.
>> Implementing it as dynamically allocated list is differently wasteful.
>> Saving several mallocs and frees can be worth "wasting" a few pages of
>> memory for a short time.
>
> Most usage of QmpInputVisitor at startup comes from
> object_property_set_qobject, which only sets small scalar objects. The
> stack is entirely unused in this case.
A quick test run shows ~300 qmp_input_visitor_new() calls during
startup, with at most two alive at the same time.
Why would it matter whether these are in the order of 150 bytes or 25000
bytes each? How could this materially impact RSS?
There's one type of waste here that I understand: we zero the whole
QmpInputVisitor on allocation.
I'm not opposed to changing how the stack is implemented, I just want to
first understand why the current implmementation behaves badly (assuming
it does).
next prev parent reply other threads:[~2016-07-04 11:18 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-28 9:01 [Qemu-devel] [PATCH 00/15] optimize Qemu RSS usage Peter Lieven
2016-06-28 9:01 ` [Qemu-devel] [PATCH 01/15] coroutine-ucontext: mmap stack memory Peter Lieven
2016-06-28 10:02 ` Peter Maydell
2016-06-28 10:21 ` Peter Lieven
2016-06-28 11:04 ` Paolo Bonzini
2016-06-28 9:01 ` [Qemu-devel] [PATCH 02/15] coroutine-ucontext: add a switch to monitor maximum stack size Peter Lieven
2016-06-28 9:01 ` [Qemu-devel] [PATCH 03/15] coroutine-ucontext: reduce stack size to 64kB Peter Lieven
2016-06-28 10:54 ` Paolo Bonzini
2016-06-28 10:57 ` Dr. David Alan Gilbert
2016-06-28 11:17 ` Peter Lieven
2016-06-28 11:35 ` Dr. David Alan Gilbert
2016-06-28 12:09 ` Peter Lieven
2016-06-28 14:20 ` Dr. David Alan Gilbert
2016-06-30 6:34 ` Peter Lieven
2016-06-28 11:13 ` Peter Lieven
2016-06-28 11:26 ` Paolo Bonzini
2016-06-28 9:01 ` [Qemu-devel] [PATCH 04/15] coroutine: add a knob to disable the shared release pool Peter Lieven
2016-06-28 10:41 ` Paolo Bonzini
2016-06-28 10:47 ` Peter Lieven
2016-06-28 9:01 ` [Qemu-devel] [PATCH 05/15] util: add a helper to mmap private anonymous memory Peter Lieven
2016-10-16 2:10 ` Michael S. Tsirkin
2016-10-18 13:50 ` Alex Bennée
2016-06-28 9:01 ` [Qemu-devel] [PATCH 06/15] exec: use mmap for subpages Peter Lieven
2016-06-28 10:48 ` Paolo Bonzini
2016-06-28 9:01 ` [Qemu-devel] [PATCH 07/15] qapi: use mmap for QmpInputVisitor Peter Lieven
2016-06-28 9:29 ` Dr. David Alan Gilbert
2016-06-28 9:39 ` Peter Lieven
2016-06-28 10:10 ` Daniel P. Berrange
2016-06-28 10:17 ` Dr. David Alan Gilbert
2016-06-28 10:21 ` Daniel P. Berrange
2016-06-28 14:10 ` Eric Blake
2016-06-28 11:36 ` Paolo Bonzini
2016-06-28 14:14 ` Eric Blake
2016-06-30 14:12 ` Markus Armbruster
2016-07-04 9:02 ` Paolo Bonzini
2016-07-04 11:18 ` Markus Armbruster [this message]
2016-07-04 11:36 ` Peter Lieven
2016-07-04 11:42 ` Paolo Bonzini
2016-06-28 9:01 ` [Qemu-devel] [PATCH 08/15] virtio: use mmap for VirtQueue Peter Lieven
2016-06-28 9:01 ` [Qemu-devel] [PATCH 09/15] loader: use mmap for ROMs Peter Lieven
2016-06-28 10:41 ` Paolo Bonzini
2016-06-28 11:26 ` Peter Lieven
2016-07-04 7:30 ` Peter Lieven
2016-06-28 9:01 ` [Qemu-devel] [PATCH 10/15] vmware_svga: use mmap for scratch pad Peter Lieven
2016-06-28 9:01 ` [Qemu-devel] [PATCH 11/15] qom: use mmap for bigger Objects Peter Lieven
2016-06-28 10:08 ` Daniel P. Berrange
2016-06-28 10:10 ` Peter Maydell
2016-06-28 10:19 ` Peter Lieven
2016-06-28 10:42 ` Paolo Bonzini
2016-06-28 10:49 ` Peter Lieven
2016-06-30 14:15 ` Markus Armbruster
2016-06-28 9:01 ` [Qemu-devel] [PATCH 12/15] util: add a function to realloc mmapped memory Peter Lieven
2016-06-28 9:01 ` [Qemu-devel] [PATCH 13/15] exec: use mmap for PhysPageMap->nodes Peter Lieven
2016-06-28 10:43 ` Paolo Bonzini
2016-06-28 10:48 ` Peter Lieven
2016-07-11 9:31 ` Peter Lieven
2016-07-11 9:44 ` Peter Lieven
2016-07-11 10:37 ` Paolo Bonzini
2016-07-12 14:34 ` Peter Lieven
2016-07-13 10:27 ` Paolo Bonzini
2016-07-14 14:47 ` Peter Lieven
2016-06-28 9:01 ` [Qemu-devel] [PATCH 14/15] vnc-tight: make the encoding palette static Peter Lieven
2016-06-28 11:12 ` Paolo Bonzini
2016-06-28 11:18 ` Peter Lieven
2016-06-28 9:01 ` [Qemu-devel] [PATCH 15/15] vnc: use mmap for VncState Peter Lieven
2016-06-28 11:37 ` [Qemu-devel] [PATCH 00/15] optimize Qemu RSS usage Paolo Bonzini
2016-06-28 12:14 ` Peter Lieven
2016-06-28 12:29 ` Paolo Bonzini
2016-06-28 12:33 ` Peter Lieven
2016-06-28 12:56 ` Paolo Bonzini
2016-06-28 12:56 ` Dr. David Alan Gilbert
2016-06-28 14:43 ` Peter Lieven
2016-06-28 14:52 ` Peter Lieven
2016-10-12 21:18 ` Michael R. Hines
2016-10-18 10:47 ` Peter Lieven
2016-10-19 17:40 ` Michael R. Hines
2016-10-31 22:00 ` Michael R. Hines
2016-11-01 22:02 ` Michael R. Hines
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