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Re: [Qemu-devel] [PATCH v2] xen_disk: add persistent grant support to xe
From: |
Roger Pau Monné |
Subject: |
Re: [Qemu-devel] [PATCH v2] xen_disk: add persistent grant support to xen_disk backend |
Date: |
Wed, 9 Jan 2013 14:13:55 +0100 |
User-agent: |
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:17.0) Gecko/17.0 Thunderbird/17.0 |
On 09/01/13 13:48, Stefano Stabellini wrote:
> On Tue, 8 Jan 2013, Roger Pau Monne wrote:
>> This protocol extension reuses the same set of grant pages for all
>> transactions between the front/back drivers, avoiding expensive tlb
>> flushes, grant table lock contention and switches between userspace
>> and kernel space. The full description of the protocol can be found in
>> the public blkif.h header.
>>
>> http://xenbits.xen.org/gitweb/?p=xen.git;a=blob_plain;f=xen/include/public/io/blkif.h
>>
>> Speed improvement with 15 guests performing I/O is ~450%.
>>
>> Signed-off-by: Roger Pau Monné <address@hidden>
>> Cc: address@hidden
>> Cc: Stefano Stabellini <address@hidden>
>> Cc: Anthony PERARD <address@hidden>
>> ---
>> Performance comparison with the previous implementation can be seen in
>> the followign graph:
>>
>> http://xenbits.xen.org/people/royger/persistent_read_qemu.png
>> ---
>> Changes since v1:
>> * Fix coding style issues.
>> * Add more comments regarding how ioreq_map works.
>
> The patch looks good now, I only have a very small stylistic comment.
>
>
>> + for (i = 0; i < ioreq->v.niov; i++) {
>> + ioreq->v.iov[i].iov_base = page[i] +
>> + (uintptr_t)ioreq->v.iov[i].iov_base;
>
> ioreq->v.iov[i].iov_base += (uintptr_t)page[i] ?
True. Would you like to fix that yourself before committing, or do you
want me to resend?
Thanks for the review.