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Issue 891335 link

Starred by 3 users
Status: Verified
Owner:
dverkamp@chromium.org
Closed: Jan 9
Cc:
smbar...@chromium.org
dgreid@chromium.org
tbuck...@chromium.org
Components:
EstimatedDays: ----
NextAction: ----
OS: Chrome
Pri: 3
Type: Bug-Regression



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crosvm qcow2 performance regression

Project Member Reported by dverkamp@chromium.org, Oct 2 
https://listnr.corp.google.com/product/208/report/85687097735

https://chromium-review.googlesource.com/1207453 introduced slowdowns in the qcow disk I/O path.

https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/1247441 (already merged) should bring performance back to where it was before.

Keeping this open for now to track a few more follow-up patches with further qcow optimizations.
Project Member

Comment 1 by bugdroid1@chromium.org, Oct 13 

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform/crosvm/+/6b28917b83a99b5638fee0931114586da1ec9dba

commit 6b28917b83a99b5638fee0931114586da1ec9dba
Author: Daniel Verkamp <dverkamp@chromium.org>
Date: Sat Oct 13 21:55:25 2018

qcow: create BufWriter with exact capacity

Rather than using the default BufWriter capacity (currently 8K),
calculate the exact size required to contain the table.  This further
consolidates the write() system calls to the minimum required.

BUG= chromium:891335 
TEST=Manually verify expected write() calls with strace

Change-Id: I9ade77024e60a92d30b65beb07c2385e5dacc167
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1250035
Reviewed-by: Dylan Reid <dgreid@chromium.org>

[modify] https://crrev.com/6b28917b83a99b5638fee0931114586da1ec9dba/qcow/src/qcow_raw_file.rs

Comment 2 by dverkamp@chromium.org, Jan 9

Status: Verified (was: Started)
Closing this since the original issue was solved by batching up writes into larger chunks.  Any other qcow2 performance regressions should get their own bugs.
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