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Re: [Qemu-devel] [V2 0/25] Async threading for VirtFS using glib threads


From: Venkateswararao Jujjuri
Subject: Re: [Qemu-devel] [V2 0/25] Async threading for VirtFS using glib threads & coroutines.
Date: Wed, 18 May 2011 11:43:47 -0700
User-agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); en-US; rv:1.9.2.17) Gecko/20110414 Thunderbird/3.1.10

On 05/18/2011 03:39 AM, Stefan Hajnoczi wrote:
On Tue, May 17, 2011 at 8:43 PM, Venkateswararao Jujjuri (JV)
<address@hidden>  wrote:

I sent comments on individual patches.  This is turning out nice, many
of the PDU handlers are now straight-line code that can be followed
easily.

Thanks. Yeah it is coming out nice. :-)

o Redesigned to use bh as per Stefan's suggestion.
  This made the code very simple but is little less performant compared to V1.
  Anthony suggested to go-in with cleaner code and design (This version) and
  deal with the performance later.
  Just to put in perspective:
  Sequential Writes of creating 1GB files using ffsb
  o Write size 8k
  With bh: 66.9MB/sec
  Without bh (marshalling routines): 74.9 MB/sec

  o Write size 128k
  With bh: 117MB/sec
  Without bh (marshalling routines): 122MB/sec
It would be interesting to hack in a post-yield callback which is
invoked after yield transfers control back to the calling coroutine.
This avoids setting up a BH and notifying the iothread to invoke it.
I'm just suggesting this as an experiment to see if the BH mechanism
causes the performance degradation, not as a real solution.

Correct, plan is to get the functionality in first and then handle this area.

Thanks,
JV

Stefan





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