A series of performance improvements for disks using the Xen PV ring.

These have had fairly extensive testing.

The batching and latency improvements together boost the throughput
of small reads and writes by two to six percent (measured using fio
in the guest)

Avoiding repeated calls to posix_memalign() reduced the dirty heap
from 25MB to 5MB in the case of a single datapath process while also
improving performance.

---

Tim Smith (3):
      Improve xen_disk batching behaviour
      Improve xen_disk response latency
      Avoid repeated memory allocation in xen_disk


 hw/block/xen_disk.c |   82 +++++++++++++++++++++++++++++----------------------
 1 file changed, 46 insertions(+), 36 deletions(-)

--
Tim Smith <tim.smith@citrix.com>

Hi,

This series seems to have some coding style problems. See output below for
more information:

Type: series
Message-id: 154115098499.664.15585399091081300567.stgit@dhcp-3-135.uk.xensource.com
Subject: [Qemu-devel] [PATCH 0/3] Performance improvements for xen_disk

=== TEST SCRIPT BEGIN ===
#!/bin/bash

BASE=base
n=1
total=$(git log --oneline $BASE.. | wc -l)
failed=0

git config --local diff.renamelimit 0
git config --local diff.renames True
git config --local diff.algorithm histogram

commits="$(git log --format=%H --reverse $BASE..)"
for c in $commits; do
    echo "Checking PATCH $n/$total: $(git log -n 1 --format=%s $c)..."
    if ! git show $c --format=email | ./scripts/checkpatch.pl --mailback -; then
        failed=1
        echo
    fi
    n=$((n+1))
done

exit $failed
=== TEST SCRIPT END ===

Updating 3c8cf5a9c21ff8782164d1def7f44bd888713384
Switched to a new branch 'test'
c6a893c90e Avoid repeated memory allocation in xen_disk
d6c377c588 Improve xen_disk response latency
d60360a117 Improve xen_disk batching behaviour

=== OUTPUT BEGIN ===
Checking PATCH 1/3: Improve xen_disk batching behaviour...
WARNING: line over 80 characters
#60: FILE: hw/block/xen_disk.c:607:
+        if (inflight_atstart > IO_PLUG_THRESHOLD && batched >= inflight_atstart) {

ERROR: spaces required around that '=' (ctx:VxV)
#67: FILE: hw/block/xen_disk.c:614:
+                batched=0;
                        ^

total: 1 errors, 1 warnings, 54 lines checked

Your patch has style problems, please review.  If any of these errors
are false positives report them to the maintainer, see
CHECKPATCH in MAINTAINERS.

Checking PATCH 2/3: Improve xen_disk response latency...
Checking PATCH 3/3: Avoid repeated memory allocation in xen_disk...
WARNING: line over 80 characters
#36: FILE: hw/block/xen_disk.c:139:
+        /* We cannot need more pages per ioreq than this, and we do re-use ioreqs,

ERROR: line over 90 characters
#39: FILE: hw/block/xen_disk.c:142:
+        ioreq->buf = qemu_memalign(XC_PAGE_SIZE, BLKIF_MAX_SEGMENTS_PER_REQUEST * XC_PAGE_SIZE);

total: 1 errors, 1 warnings, 50 lines checked

Your patch has style problems, please review.  If any of these errors
are false positives report them to the maintainer, see
CHECKPATCH in MAINTAINERS.

=== OUTPUT END ===

Test command exited with code: 1


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