Bug 865858

Summary:

Potentially unnecessary file opens/closes performed around xattr read/writes

Product:

[Community] Gluster-Swift

Reporter:

Peter Portante <pportant>

Component:

utils

Assignee:

Nobody <nobody>

Status:

MODIFIED ---

QA Contact:

Severity:

low

Docs Contact:

Priority:

low

Version:

1.8.0

CC:

bugs, perfbz, pportant

Target Milestone:

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Target Release:

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Hardware:

x86_64

OS:

Linux

Whiteboard:

Fixed In Version:

Doc Type:

Bug Fix

Doc Text:

Story Points:

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Clone Of:

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Last Closed:

Type:

Bug

Regression:

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Documentation:

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oVirt Team:

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RHEL 7.3 requirements from Atomic Host:

Cloudforms Team:

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Target Upstream Version:

Embargoed:

Bug Depends On:

Bug Blocks:

903396, 978061

Attachments:

Description	Flags
Initial patch to remove the use of deprecated pyxattr methods.	none
Actual fix to remove extra system calls.	none

Description Peter Portante 2012-10-12 16:36:18 UTC

Description of problem:

  The Gluster/Swift plugin code provides wrappers for get/set/removexattr
  system calls which perform file open/close systems calls. The open/close
  sequence appears to be unnecessary.

Version-Release number of selected component (if applicable):

  3.3.0

Actual results:

  Files are first opened, xattr key read/written/removed, then closed for
  every metadata key stored (could have multiple keys stored, see
  https://bugzilla.redhat.com/show_bug.cgi?id=865619)

Expected results:

  No open or close system call is made around xattr operations.

Comment 1 Peter Portante 2012-10-12 18:34:07 UTC

I created a permanent pastebin link with the output of an strace from a GET on an object.

Lines 222 - 240 are annotated to show where a read_metadata() calls starts and ends, and what do_getxattr() does for a file. Notice that 13 system calls are made. The two calls to fgetxattr in a row are the result of the pyxattr modules' behavior to first find out the size of the xattr value so that it can allocate memory for it and then fetch the full contents of it.

We should be able to remove the extra stat calls as well.

Comment 2 Peter Portante 2012-10-12 18:51:18 UTC

Probably would be helpful to actually include the link to the pastebin ...

http://pastebin.test.redhat.com/110804

Comment 3 Peter Portante 2012-10-12 19:10:11 UTC

Here are the results of the same operation but with a patch applied to remove the extra system calls (from 13 down to 3).

http://pastebin.test.redhat.com/110818

Comment 4 Peter Portante 2012-10-12 19:11:21 UTC

Created attachment 626189 [details]
Initial patch to remove the use of deprecated pyxattr methods.

Comment 5 Peter Portante 2012-10-12 19:12:00 UTC

Created attachment 626190 [details]
Actual fix to remove extra system calls.

Comment 6 Vijay Bellur 2012-10-13 17:40:51 UTC

CHANGE: http://review.gluster.org/4077 (Refactor to use pyxattr's get/set/remove methods) merged in master by Anand Avati (avati)

Comment 7 Vijay Bellur 2012-10-13 17:45:00 UTC

CHANGE: http://review.gluster.org/4078 (Fix BZ 865858: remove unnecessary system calls around xattr ops) merged in master by Anand Avati (avati)