[Gluster-devel] Reduce memcpy in glfs read and write

[Milind Changire]

Would https://bugzilla.redhat.com/show_bug.cgi?id=1233136 be related to
Sachin's problem?

Milind

On 06/21/2016 06:28 PM, Pranith Kumar Karampuri wrote:
> 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 at commvault.com
> <mailto:spandit at commvault.com>> 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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