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From: Markus Armbruster <armbru@redhat.com>
To: Claudio Fontana <cfontana@suse.de>
Cc: Thomas Huth <thuth@redhat.com>,
	Eduardo Habkost <ehabkost@redhat.com>,
	Richard Henderson <richard.henderson@linaro.org>,
	qemu-devel@nongnu.org, Roman Bolshakov <r.bolshakov@yadro.com>,
	Gerd Hoffmann <kraxel@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH v2 2/6] accel: accel_available() function
Date: Fri, 27 Nov 2020 15:45:37 +0100	[thread overview]
Message-ID: <87y2imq2ni.fsf@dusky.pond.sub.org> (raw)
In-Reply-To: <55ed249f-9fd3-fe3d-c63a-8d74803a72ca@suse.de> (Claudio Fontana's message of "Fri, 27 Nov 2020 10:04:37 +0100")

Claudio Fontana <cfontana@suse.de> writes:

> On 11/26/20 10:48 PM, Eduardo Habkost wrote:
>> On Thu, Nov 26, 2020 at 10:06:03PM +0100, Claudio Fontana wrote:
>>> On 11/26/20 3:25 PM, Paolo Bonzini wrote:
>>>> On 26/11/20 15:13, Claudio Fontana wrote:
>>>>> One option I see is simply to document the behavior where
>>>>> accel_available() is declared in accel.h (ie do not use in fast
>>>>> path), as well as in accel_find() actually, so that both accel_find()
>>>>> and accel_available() are avoided in fast path and avoid being called
>>>>> frequently at runtime.
>>>>>
>>>>> Another option could be to remove the allocation completely, and use
>>>>> for example accel_find(ACCEL_CLASS_NAME("tcg")), or another option
>>>>> again would be to remove the allocation and use either a fixed buffer
>>>>> + snprintf, or alloca -like builtin code to use the stack, ...
>>>>>
>>>>> Not a big deal, but with a general utility and short name like
>>>>> accel_available(name) it might be tempting to use this more in the
>>>>> future?
>>>>
>>>> I think it's just that the usecase is not that common.  "Is this 
>>>> accelerator compiled in the binary" is not something you need after 
>>>> startup (or if querying the monitor).
>>>>
>>>> Paolo
>>>>
>>>>
>>>
>>> A script that repeatedly uses the QMP interface to query for
>>> the status could generate fragmentation this way I think.
>> 
>> Is this a problem?  Today, execution of a "query-kvm" command
>> calls g_malloc() 37 times.
>> 
>
> Not ideal in my view, but not the end of the world either.

QMP's appetite for malloc is roughly comparable to a pig's for truffles.



  reply	other threads:[~2020-11-27 14:47 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-25 20:56 [PATCH v2 0/6] arch_init.c cleanup Eduardo Habkost
2020-11-25 20:56 ` [PATCH v2 1/6] arch_init: Move QEMU_ARCH definitions to cpu.h Eduardo Habkost
2020-11-25 20:56   ` Eduardo Habkost
2020-11-26 12:31   ` Thomas Huth
2020-11-26 12:31     ` Thomas Huth
2020-11-27 11:35   ` Cornelia Huck
2020-11-27 11:35     ` Cornelia Huck
2020-11-25 20:56 ` [PATCH v2 2/6] accel: accel_available() function Eduardo Habkost
2020-11-26  9:14   ` Claudio Fontana
2020-11-26 13:36     ` Eduardo Habkost
2020-11-26 14:13       ` Claudio Fontana
2020-11-26 14:25         ` Paolo Bonzini
2020-11-26 21:06           ` Claudio Fontana
2020-11-26 21:48             ` Eduardo Habkost
2020-11-27  9:04               ` Claudio Fontana
2020-11-27 14:45                 ` Markus Armbruster [this message]
2020-11-27 14:58                   ` Claudio Fontana
2020-11-27 16:47                     ` Markus Armbruster
2020-11-27  5:00             ` Paolo Bonzini
2020-11-27 12:08   ` Cornelia Huck
2020-11-25 20:56 ` [PATCH v2 3/6] kvm: Remove kvm_available() function Eduardo Habkost
2020-11-25 20:56   ` Eduardo Habkost
2020-11-27 12:10   ` Cornelia Huck
2020-11-27 12:10     ` Cornelia Huck
2020-11-25 20:56 ` [PATCH v2 4/6] xen: Delete xen_available() function Eduardo Habkost
2020-11-25 20:56   ` Eduardo Habkost
2020-11-27 12:11   ` Cornelia Huck
2020-11-27 12:11     ` Cornelia Huck
2020-11-27 14:52   ` Anthony PERARD via
2020-11-27 14:52     ` Anthony PERARD
2020-11-25 20:56 ` [PATCH v2 5/6] Remove unnecessary usage of arch_init.h Eduardo Habkost
2020-11-25 20:56   ` Eduardo Habkost
2020-11-27 12:23   ` Cornelia Huck
2020-11-27 12:23     ` Cornelia Huck
2020-11-25 20:56 ` [PATCH v2 6/6] Rename arch_init.h to arch_type.h Eduardo Habkost
2020-11-27 12:25   ` Cornelia Huck
2020-11-25 22:23 ` [PATCH v2 0/6] arch_init.c cleanup Roman Bolshakov

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