From: Kevin Constantine Subject: Re: [PATCH 2/2] nfs-iostat.py: Added bytes written output Date: Tue, 21 Apr 2009 13:39:26 -0700 Message-ID: <49EE2EFE.7050300@disney.com> References: <1240279414-30528-1-git-send-email-kevin.constantine@disneyanimation.com> <1240279414-30528-2-git-send-email-kevin.constantine@disneyanimation.com> <1240279414-30528-3-git-send-email-kevin.constantine@disneyanimation.com> <49EE0901.2040704@disney.com> <981BA943-47FA-433D-A762-B83983E6532A@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: linux-nfs@vger.kernel.org To: Chuck Lever Return-path: Received: from mailgate1.disneyanimation.com ([12.188.26.101]:64620 "EHLO mailgate1.disneyanimation.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752849AbZDUUj2 (ORCPT ); Tue, 21 Apr 2009 16:39:28 -0400 In-Reply-To: <981BA943-47FA-433D-A762-B83983E6532A@oracle.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: Chuck Lever wrote: > On Apr 21, 2009, at 1:57 PM, Kevin Constantine wrote: >> Chuck Lever wrote: >>> On Apr 20, 2009, at 10:03 PM, Kevin Constantine wrote: >>>> Print statistics about bytes written by NFS >>>> >>>> Signed-off-by: Kevin Constantine >>>> >>>> --- >>>> tools/nfs-iostat/nfs-iostat.py | 10 ++++++++++ >>>> 1 files changed, 10 insertions(+), 0 deletions(-) >>>> >>>> diff --git a/tools/nfs-iostat/nfs-iostat.py >>>> b/tools/nfs-iostat/nfs-iostat.py >>>> index d331a72..5f2e232 100644 >>>> --- a/tools/nfs-iostat/nfs-iostat.py >>>> +++ b/tools/nfs-iostat/nfs-iostat.py >>>> @@ -221,6 +221,7 @@ class DeviceData: >>>> """ >>>> nfs_stats = self.__nfs_data >>>> app_bytes_read = float(nfs_stats['normalreadbytes'] + >>>> nfs_stats['directreadbytes']) >>>> + bytes_written_by_app = float(nfs_stats['normalwritebytes'] >>>> + nfs_stats['directwritebytes']) >>>> if app_bytes_read != 0: >>>> read_bytes_from_server = float(nfs_stats['serverreadbytes']) >>>> directio_bytes_from_server = >>>> float(nfs_stats['directreadbytes']) >>>> @@ -234,6 +235,15 @@ class DeviceData: >>>> cached_read_bytes / 1024.0 / 1024.0, \ >>>> app_bytes_read / 1024.0 / 1024.0, \ >>>> ratio) >>>> + if bytes_written_by_app != 0: >>>> + bytes_written_by_nfs = float(nfs_stats['serverwritebytes']) >>>> + cached_write_bytes = float(bytes_written_by_app - >>>> bytes_written_by_nfs); >>> Again, I don't see why this computation is necessary: The >>> "normalwritebytes" statistic is what was written through the client's >>> cache, and "directwritebytes" counts the number of bytes that were >>> written via O_DIRECT. >> >> As I said in the email preceding these patches: >> "I'm not quire sure about this patch. I'm seeing oddities where the >> number of bytes in "NORMALWRITTENBYTES + DIRECTWRITTENBYTES" does not >> equal SERVERWRITTENBYTES. In some cases the amount of data written by >> the app (normalwrittenbytes + directwrittenbytes) is greater than the >> amount of data written to the server, and in other cases it's less >> than the amount of data written to the server. At the moment, i've >> ascribed that difference to data being written to the local cache and >> not flushed, but that doesn't make a whole lot of sense." > > Our e-mail system may have barfed on my earlier reply, but I would like > to understand why you need this statistic. What kind of analysis are > you looking for on the write side? > As far as writes go, all I really wanted to print is MB being written to the nfs server. But I noticed along the way that the values don't add up and found it odd. An application writing data to an nfs server should be getting counted by either normalwrittenbytes, or directwrittenbytes. The data being written by the nfs by an NFS write request should be counted by serverwrittenbytes. normal + direct should equal server, but it doesn't, and I'm wondering what happened to those bytes. Sometimes normal + direct > server, sometimes normal + direct < server. What I have in the patch doesn't really matter because I don't understand the imbalance in the counters. -kevin >> >>>> + print >>>> + print '%13s %12s %15s %15s' % ("Data Written:", "To >>>> Server", "To Cache", "Total") >>>> + print '%10s %13.4fMB %13.4fMB %13.4fMB' % ("", \ >>>> + bytes_written_by_nfs / 1024.0 / 1024.0, \ >>>> + cached_write_bytes / 1024.0 / 1024.0, \ >>>> + bytes_written_by_app / 1024.0 / 1024.0) >>>> >>>> def __print_attr_cache_stats(self, sample_time): >>>> """Print attribute cache efficiency stats > > -- > Chuck Lever > chuck[dot]lever[at]oracle[dot]com