Re: Reduce memcpy in glfs read and write

[Pranith Kumar Karampuri <pkarampu@xxxxxxxxxx>]

Hey!!

       Hope you are doing good. I took a look at the bt. So when flush comes write-behind has to flush all the writes down. I see the following frame hung in iob_unref:
Thread 7 (Thread 0x7fa601a30700 (LWP 16218)):
#0  0x00007fa60cc55225 in pthread_spin_lock () from /lib64/libpthread.so.0  <<---- Does it always hang there?
#1  0x00007fa60e1f373e in iobref_unref (iobref=0x19dc7e0) at iobuf.c:907
#2  0x00007fa60e246fb2 in args_wipe (args=0x19e70ec) at default-args.c:1593
#3  0x00007fa60e1ea534 in call_stub_wipe_args (stub=0x19e709c) at call-stub.c:2466
#4  0x00007fa60e1ea5de in call_stub_destroy (stub=0x19e709c) at call-stub.c:2482

Is this on top of master branch? It seems like we missed an unlock of the spin-lock or the iobref has junk value which gives the feeling that it is in locked state (May be double free?). Do you have any extra patches you have in your repo which make changes in iobuf?

On Tue, Jun 21, 2016 at 4:07 AM, Sachin Pandit <spandit@xxxxxxxxxxxxx> wrote:

Hi all,

 

I bid adieu to you all with the hope of crossing path again, and the time has come rather quickly. It feels great to work on GlusterFS again.

               

Currently we are trying to write data backed up by Commvault Simpana to glusterfs volume (Disperse volume). To improve the performance, I have implemented the proposal put forward my Rafi  K C [1]. I have some questions regarding libgfapi and iobuf pool.

 

To reduce an extra level of copy in glfs read and write, I have implemented few APIs to request a buffer (similar to the one represented in  [1]) from iobuf pool which can be used by the application to write data to. With this implementation, when I try to reuse the buffer for consecutive writes, I could see a hang in syncop_flush of glfs_close (BT of the hang can be found in [2]). I wanted to know if reusing the buffer is recommended. If not, do we need to request buffer for each writes?

 

Setup : Distributed-Disperse ( 4 * (2+1)). Bricks scattered over 3 nodes.

 

[1] http://www.gluster.org/pipermail/gluster-devel/2015-February/043966.html

[2] Attached file -  bt.txt

 

Thanks & Regards,

Sachin Pandit.

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Pranith

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