From: David Hildenbrand <david@redhat.com>
To: Michael Kelley <mhklinux@outlook.com>,
"haiyangz@microsoft.com" <haiyangz@microsoft.com>,
"wei.liu@kernel.org" <wei.liu@kernel.org>,
"decui@microsoft.com" <decui@microsoft.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>
Subject: Re: [PATCH 1/1] hv_balloon: Enable hot-add for memblock sizes > 128 Mbytes
Date: Tue, 30 Apr 2024 10:52:50 +0200 [thread overview]
Message-ID: <c911ab92-1bec-4e5d-9bc8-5a6044f4948b@redhat.com> (raw)
In-Reply-To: <SN6PR02MB4157D5BB1C140D229875AB50D41B2@SN6PR02MB4157.namprd02.prod.outlook.com>
On 29.04.24 17:30, Michael Kelley wrote:
> From: Michael Kelley <mhklinux@outlook.com> Sent: Friday, April 26, 2024 9:36 AM
>>>> @@ -505,8 +505,9 @@ enum hv_dm_state {
>>>>
>>>> static __u8 recv_buffer[HV_HYP_PAGE_SIZE];
>>>> static __u8 balloon_up_send_buffer[HV_HYP_PAGE_SIZE];
>>>> +static unsigned long ha_chunk_pgs;
>>>
>>> Why not stick to PAGES_IN_2M and call this
>>>
>>> ha_pages_in_chunk? Much easier to get than "pgs".
>>
>> OK. I was trying to keep the new identifier short so that
>> mechanically substituting it for HA_CHUNK didn't blow up
>> the line length.
>>
>>>
>>> Apart from that looks good. Some helper macros to convert size to chunks
>>> etc. might make the code even more readable.
>>
>> I'll look at this. Might help the line length problem too.
>>
>
> I didn't see any particular complexity in converting size to chunks. But
> this slightly opaque sequence is repeated in three places:
>
> new_inc = (residual / HA_CHUNK) * HA_CHUNK;
> if (residual % HA_CHUNK)
> new_inc += HA_CHUNK;
>
> If HA_CHUNK (or the new memblock size based variable) is a
> power of 2, then these can become:
>
> new_inc = ALIGN(residual, HA_CHUNK);
>
> which is a lot better. I'll make that change, and a couple of other
> changes where things are open coded that could be existing
> kernel macros.
Cool! Make sure to CC me on v2.
>
> Question: Is memblock size guaranteed to be a power of 2? It looks
> to be so in the x86 code, but I can't tell on s390 and ppc. For safety,
> I'll add a check in the Hyper-V balloon driver init code, as the
> communication with Hyper-V expects a power of 2.
Yes, in memory_dev_init() we make sure that the size is a power of 2,
and if it is not, we would panic().
--
Cheers,
David / dhildenb
prev parent reply other threads:[~2024-04-30 8:52 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-11 18:12 [PATCH 1/1] hv_balloon: Enable hot-add for memblock sizes > 128 Mbytes mhkelley58
2024-04-25 14:31 ` Michael Kelley
2024-04-26 8:58 ` David Hildenbrand
2024-04-26 16:35 ` Michael Kelley
2024-04-29 15:30 ` Michael Kelley
2024-04-30 8:52 ` David Hildenbrand [this message]
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