On 11 Dec 2020, at 11:38, Patargias, George (STFC,RAL,SC) <[log in to unmask]> wrote:
Thanks for the reply.
Indeed, I couldn't find any flag from the client side that invokes a vector read, so I meant the server side.
Basically, I am trying to figure out how XrdCl::File::VectorRead is invoked and what is the subsequent sequence of calls that results in the construction of the XrdOucIOVec structure (XrdOuc/XrdOucIOVec.hh) that will be passed asan argument to the ReadV(XrdOucIOVec *readV, int rdvcnt) function in XrdOss/XrdOss.cc.
So, any clues on the relation between XrdCl::File::VectorRead and XrdOssDF::ReadV would be very useful.
From: Bockelman, Brian <[log in to unmask]>
Sent: 10 December 2020 22:57
To: Patargias, George (STFC,RAL,SC) <[log in to unmask]>
Cc: [log in to unmask] <[log in to unmask]>; [log in to unmask] <[log in to unmask]>; Johnson, Ian (STFC,RAL,SC) <[log in to unmask]>
Subject: Re: Handling of vector-reads in the the XRootDHi George,
Did you mean in the client or server side?
In the client, XrdCl::File::VectorRead is what is invoked by various applications (e.g., ROOT) in order to trigger a vector read.
I don't believe xrdcp ever invokes a vector read.
> On Dec 10, 2020, at 11:35 AM, Patargias, George (STFC,RAL,SC) <[log in to unmask]> wrote:
> Me and Ian are working in RAL on the implementation of vector reads in the XRootD Ceph plugin.
> Can you please point us to the part of the XRootD code (XrdCl or...) that groups many individual small reads from the same
> file into a single vector (XrdOucIOVec) which is eventually passed to the ReadV(XrdOucIOVec *readV, int rdvcnt) function
> in XrdOss/XrdOss.cc?
> Is this vectorisation enabled by default in the case of many reads from the same file (didn't see any xrdcp flag that serves this purpose)?
> Many thanks,
> George Patargias
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