[Qemu-devel] [PATCH 1.8 3/6] qemu-img: add option to specify alternate iobuffer size

[Peter Lieven <pl@kamp.de>]

since the convert process is basically a sync operation it might
be benificial in some case to change the hardcoded I/O buffer
size to an alternate (greater) value.

Signed-off-by: Peter Lieven <pl@kamp.de>
---
 qemu-img-cmds.hx |    4 ++--
 qemu-img.c       |   25 ++++++++++++++++++++-----
 qemu-img.texi    |    4 +++-
 3 files changed, 25 insertions(+), 8 deletions(-)

diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx
index da1d965..e0b8ab4 100644
--- a/qemu-img-cmds.hx
+++ b/qemu-img-cmds.hx
@@ -34,9 +34,9 @@ STEXI
 ETEXI
 
 DEF("convert", img_convert,
-    "convert [-c] [-p] [-q] [-n] [-f fmt] [-t cache] [-O output_fmt] [-o options] [-s snapshot_name] [-S sparse_size] filename [filename2 [...]] output_filename")
+    "convert [-c] [-p] [-q] [-n] [-f fmt] [-t cache] [-O output_fmt] [-o options] [-s snapshot_name] [-S sparse_size] [-m iobuf_size] filename [filename2 [...]] output_filename")
 STEXI
-@item convert [-c] [-p] [-q] [-n] [-f @var{fmt}] [-t @var{cache}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_name}] [-S @var{sparse_size}] @var{filename} [@var{filename2} [...]] @var{output_filename}
+@item convert [-c] [-p] [-q] [-n] [-f @var{fmt}] [-t @var{cache}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_name}] [-S @var{sparse_size}] [-m @var{iobuf_size}] @var{filename} [@var{filename2} [...]] @var{output_filename}
 ETEXI
 
 DEF("info", img_info,
diff --git a/qemu-img.c b/qemu-img.c
index e2d1a0a..0ce5d14 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -105,6 +105,7 @@ static void help(void)
            "       conversion. If the number of bytes is 0, the source will not be scanned for\n"
            "       unallocated or zero sectors, and the destination image will always be\n"
            "       fully allocated\n"
+           "  '-m' specify I/O buffer size in bytes (default 2M)\n"
            "  '--output' takes the format in which the output must be done (human or json)\n"
            "  '-n' skips the target volume creation (useful if the volume is created\n"
            "       prior to running qemu-img)\n"
@@ -1135,6 +1136,7 @@ static int img_convert(int argc, char **argv)
             sector_num_next_status = 0;
     uint64_t bs_sectors;
     uint8_t * buf = NULL;
+    size_t bufsectors = IO_BUF_SIZE / BDRV_SECTOR_SIZE;
     const uint8_t *buf1;
     BlockDriverInfo bdi;
     QEMUOptionParameter *param = NULL, *create_options = NULL;
@@ -1152,7 +1154,7 @@ static int img_convert(int argc, char **argv)
     compress = 0;
     skip_create = 0;
     for(;;) {
-        c = getopt(argc, argv, "f:O:B:s:hce6o:pS:t:qn");
+        c = getopt(argc, argv, "f:O:B:s:hce6o:pS:m:t:qn");
         if (c == -1) {
             break;
         }
@@ -1200,6 +1202,19 @@ static int img_convert(int argc, char **argv)
             min_sparse = sval / BDRV_SECTOR_SIZE;
             break;
         }
+        case 'm':
+        {
+            int64_t sval;
+            char *end;
+            sval = strtosz_suffix(optarg, &end, STRTOSZ_DEFSUFFIX_B);
+            if (sval < BDRV_SECTOR_SIZE || *end) {
+                error_report("Invalid I/O buffer size specified");
+                return 1;
+            }
+
+            bufsectors = sval / BDRV_SECTOR_SIZE;
+            break;
+        }
         case 'p':
             progress = 1;
             break;
@@ -1371,7 +1386,7 @@ static int img_convert(int argc, char **argv)
     bs_i = 0;
     bs_offset = 0;
     bdrv_get_geometry(bs[0], &bs_sectors);
-    buf = qemu_blockalign(out_bs, IO_BUF_SIZE);
+    buf = qemu_blockalign(out_bs, bufsectors * BDRV_SECTOR_SIZE);
 
     if (skip_create) {
         int64_t output_length = bdrv_getlength(out_bs);
@@ -1394,7 +1409,7 @@ static int img_convert(int argc, char **argv)
             goto out;
         }
         cluster_size = bdi.cluster_size;
-        if (cluster_size <= 0 || cluster_size > IO_BUF_SIZE) {
+        if (cluster_size <= 0 || cluster_size > bufsectors * BDRV_SECTOR_SIZE) {
             error_report("invalid cluster size");
             ret = -1;
             goto out;
@@ -1531,8 +1546,8 @@ static int img_convert(int argc, char **argv)
                 sector_num_next_status = sector_num + n1;
             }
 
-            if (nb_sectors >= (IO_BUF_SIZE / 512)) {
-                n = (IO_BUF_SIZE / 512);
+            if (nb_sectors >= bufsectors) {
+                n = bufsectors;
             } else {
                 n = nb_sectors;
             }
diff --git a/qemu-img.texi b/qemu-img.texi
index da36975..87f9d0f 100644
--- a/qemu-img.texi
+++ b/qemu-img.texi
@@ -179,7 +179,7 @@ Error on reading data
 
 @end table
 
-@item convert [-c] [-p] [-n] [-f @var{fmt}] [-t @var{cache}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_name}] [-S @var{sparse_size}] @var{filename} [@var{filename2} [...]] @var{output_filename}
+@item convert [-c] [-p] [-n] [-f @var{fmt}] [-t @var{cache}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_name}] [-S @var{sparse_size}] [-m @var{iobuf_size}] @var{filename} [@var{filename2} [...]] @var{output_filename}
 
 Convert the disk image @var{filename} or a snapshot @var{snapshot_name} to disk image @var{output_filename}
 using format @var{output_fmt}. It can be optionally compressed (@code{-c}
@@ -199,6 +199,8 @@ conversion. If @var{sparse_size} is 0, the source will not be scanned for
 unallocated or zero sectors, and the destination image will always be
 fully allocated.
 
+@var{iobuf_size} indicates the size of the I/O buffer (defaults to 2M).
+
 You can use the @var{backing_file} option to force the output image to be
 created as a copy on write image of the specified base image; the
 @var{backing_file} should have the same content as the input's base image,
-- 
1.7.9.5