Re: [PATCH v3 3/3] NFSD: Add support for encoding multiple segments

From: Anna Schumaker <Anna.Schumaker@netapp.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: "J. Bruce Fields" <bfields@fieldses.org>,
	Marc Eshel <eshel@us.ibm.com>,
	"linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>,
	<linux-nfs-owner@vger.kernel.org>, <xfs@oss.sgi.com>
Subject: Re: [PATCH v3 3/3] NFSD: Add support for encoding multiple segments
Date: Thu, 26 Mar 2015 11:21:41 -0400	[thread overview]
Message-ID: <55142405.3090000@Netapp.com> (raw)
In-Reply-To: <20150324174916.GA28906@infradead.org>

Here are my updated numbers!  I tested with files 5G in size: one 100% data, one 100% hole, and one alternating between hole and data every 4K.  I collected data for both v4.1 and v4.2 with and without the READ_PLUS patches:

##########################
#                        #
#   Without READ_PLUS    #
#                        #
##########################

NFS v4.1:
                            Trial
|---------|---------|---------|---------|---------|---------|---------|
|         |    1    |    2    |    3    |    4    |    5    | Average |
|---------|---------|---------|---------|---------|---------|---------|
|    Data |  8.723s |  7.243s |  8.252s |  6.997s |  6.980s |  7.639s |
|    Hole |  5.271s |  5.224s |  5.060s |  4.897s |  5.321s |  5.155s |
|   Mixed |  8.050s | 10.057s |  7.919s |  8.060s |  9.557s |  8.729s |
|---------|---------|---------|---------|---------|---------|---------|

NFS v4.2:
                            Trial
|---------|---------|---------|---------|---------|---------|---------|
|         |    1    |    2    |    3    |    4    |    5    | Average |
|---------|---------|---------|---------|---------|---------|---------|
|    Data |  6.707s |  7.070s |  6.722s |  6.761s |  6.810s |  6.814s |
|    Hole |  5.152s |  5.149s |  5.213s |  5.206s |  5.312s |  5.206s |
|   Mixed |  7.979s |  7.985s |  8.177s |  7.772s |  8.280s |  8.039s |
|---------|---------|---------|---------|---------|---------|---------|

#######################
#                     #
#   With READ_PLUS    #
#                     #
#######################

NFS v4.1:
                            Trial
|---------|---------|---------|---------|---------|---------|---------|
|         |    1    |    2    |    3    |    4    |    5    | Average |
|---------|---------|---------|---------|---------|---------|---------|
|    Data |  9.082s |  7.008s |  7.116s |  6.771s |  7.902s |  7.576s |
|    Hole |  5.333s |  5.358s |  5.380s |  5.161s |  5.282s |  5.303s |
|   Mixed |  8.189s |  8.308s |  9.540s |  7.937s |  8.420s |  8.479s |
|---------|---------|---------|---------|---------|---------|---------|

NFS v4.2:
                            Trial
|---------|---------|---------|---------|---------|---------|---------|
|         |    1    |    2    |    3    |    4    |    5    | Average |
|---------|---------|---------|---------|---------|---------|---------|
|    Data |  7.033s |  6.829s |  7.025s |  6.873s |  7.134s |  6.979s |
|    Hole |  1.794s |  1.800s |  1.905s |  1.811s |  1.725s |  1.807s |
|   Mixed |  7.590s |  8.777s |  9.423s | 10.366s |  8.024s |  8.836s |
|---------|---------|---------|---------|---------|---------|---------|

On 03/24/2015 01:49 PM, Christoph Hellwig wrote:
> On Tue, Mar 24, 2015 at 08:43:31AM -0400, Anna Schumaker wrote:
>>> I don't know, and don't have profiles.  I'll either try to reproduce or
>>> wait till Anna's back from vacation.
>>
>> I'm using whatever functions NFSD already uses for reading files,
>> which I expect go through the VFS.  Is there a flag that controls
>> cache behavior?
> 
> There's the O_DIRECT flag, but that's not what I mean.  If you just
> wrote to it it's a cached read, if you did unmount the filesystem after
> writing, or did an echo to /proc/sys/vm/drop_caches you get uncached
> read behavior.
> 