59 lines
1.9 KiB
Diff
59 lines
1.9 KiB
Diff
From 558dc7d84b46a1924e06808caa8b113238961fd3 Mon Sep 17 00:00:00 2001
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From: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
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Date: Mon, 26 Sep 2016 17:07:41 +0200
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Subject: [PATCH 08/11] Improve memory management of nbdkit python plugin
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example
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Hi,
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the nbdkit python plugin example has suboptimal memory management:
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- it creates the disk image as a string on init
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- it casts the string to bytearray on every read
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- it copies the string before and the string after the written region,
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then reassembles those pieces together with the written region to a new
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disk image string
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This is not a problem as long as the image is small, but in my tests
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with a 5 GB sized image nbdkit already used 15 GB RAM directly after
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startup, and even more (20-25 GB) on the first write.
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This changes the code to use bytearray everywhere and use the proper
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methods to change bytearray objects directly. With the patch applied,
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nbdkit with a 5 GB image will still only use 5 GB RAM even during heavy
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read/write activity.
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Regards,
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Carl-Daniel
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---
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plugins/python/example.py | 6 +++---
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1 file changed, 3 insertions(+), 3 deletions(-)
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diff --git a/plugins/python/example.py b/plugins/python/example.py
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index aa099eb..184896e 100644
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--- a/plugins/python/example.py
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+++ b/plugins/python/example.py
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@@ -29,7 +29,7 @@
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# reconnect to the same server you should see the same disk. You
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# could also put this into the handle, so there would be a fresh disk
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# per handle.
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-disk = "\0" * (1024*1024);
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+disk = bytearray(1024 * 1024)
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# This just prints the extra command line parameters, but real plugins
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# should parse them and reject any unknown parameters.
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@@ -50,9 +50,9 @@ def get_size(h):
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def pread(h, count, offset):
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global disk
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- return bytearray (disk[offset:offset+count])
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+ return disk[offset:offset+count]
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def pwrite(h, buf, offset):
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global disk
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end = offset + len (buf)
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- disk = disk[:offset] + buf + disk[end:]
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+ disk[offset:end] = buf
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--
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2.7.4
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