linux-kernel - Re: [Xen-devel] Backport request to stable of two performance related fixes for xen-blkfront (3.13 fixes to earlier trees)

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Date:	Tue, 20 May 2014 13:41:10 +0200
From:	Vitaly Kuznetsov <vkuznets@...hat.com>
To:	Roger Pau Monné <roger.pau@...rix.com>
Cc:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, axboe@...nel.dk,
	felipe.franciosi@...rix.com, gregkh@...uxfoundation.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	jerry.snitselaar@...cle.com, xen-devel@...ts.xenproject.org
Subject: Re: [Xen-devel] Backport request to stable of two performance related fixes for xen-blkfront (3.13 fixes to earlier trees)

Roger Pau Monné <roger.pau@...rix.com> writes:

> On 20/05/14 11:54, Vitaly Kuznetsov wrote:
>> Vitaly Kuznetsov <vkuznets@...hat.com> writes:
>> 
>>> 1) ramdisks (/dev/ram*) (persistent grants and indirect descriptors
>>> disabled)
>> 
>> sorry, there was a typo. persistent grants and indirect descriptors are
>> enabled with ramdisks, otherwise such testing won't make any sense.
>
> I'm not sure how is that possible, from your description I get that you
> are using 3.11 on the Dom0, which means blkback has support for
> persistent grants and indirect descriptors, but the guest is RHEL7,
> that's using the 3.10 kernel AFAICT, and this kernel only has persistent
> grants implemented.

RHEL7 kernel is mostly merged with 3.11 in its Xen part, we have
indirect descriptors backported.

Actually I tried my tests with upstream (Fedora) kernel and results were
similar. I can try comparing e.g. 3.11.10 with 3.12.0 and provide exact
measurements.

-- 
  Vitaly
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