On 2/27/14, 3:45 AM, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
>
> Recent changes to the log size scaling have resulted in using the
> default size multiplier for the log size even on small filesystems.
> Commit 88cd79b ("xfs: Add xfs_log_rlimit.c") changed the calculation
> of the maximum transaction size that the kernel would issues and
> that significantly increased the minimum size of the default log.
> As such the size of the log on small filesystems was typically
> larger than the prefious default, even though the previous default
> was still larger than the minimum needed.
>
> Rework the default log size calculation such that it will use the
> original log size default if it is larger than the minimum log size
> required, and only use a larger log if the configuration of the
> filesystem requires it.
>
> This is especially obvious in xfs/216, where the default log size is
> 10MB all the way up to 16GB filesystems. The current mkfs selects a
> log size of 50MB for the same size filesystems and this is
> unnecessarily large.
>
> Return the scaling of the log size for small filesystems to
> something similar to what xfs/216 expects.
>
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
Looks good.
Reviewed-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> ---
> mkfs/xfs_mkfs.c | 48 ++++++++++++++++++++++++++++--------------------
> 1 file changed, 28 insertions(+), 20 deletions(-)
>
> diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
> index d82128c..f7cf394 100644
> --- a/mkfs/xfs_mkfs.c
> +++ b/mkfs/xfs_mkfs.c
> @@ -2366,32 +2366,40 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
> } else if (!loginternal && !xi.logdev) {
> logblocks = 0;
> } else if (loginternal && !logsize) {
> - /*
> - * With a 2GB max log size, default to maximum size
> - * at 4TB. This keeps the same ratio from the older
> - * max log size of 128M at 256GB fs size. IOWs,
> - * the ratio of fs size to log size is 2048:1.
> - */
> - logblocks = (dblocks << blocklog) / 2048;
> - logblocks = logblocks >> blocklog;
> - logblocks = MAX(min_logblocks, logblocks);
>
> - /*
> - * If the default log size doesn't fit in the AG size, use the
> - * minimum log size instead. This ensures small filesystems
> - * don't use excessive amounts of space for the log.
> - */
> - if (min_logblocks * XFS_DFL_LOG_FACTOR >= agsize) {
> + if (dblocks < GIGABYTES(1, blocklog)) {
> + /* tiny filesystems get minimum sized logs. */
> logblocks = min_logblocks;
> + } else if (dblocks < GIGABYTES(16, blocklog)) {
> +
> + /*
> + * For small filesystems, we want to use the
> + * XFS_MIN_LOG_BYTES for filesystems smaller than 16G if
> + * at all possible, ramping up to 128MB at 256GB.
> + */
> + logblocks = MIN(XFS_MIN_LOG_BYTES >> blocklog,
> + min_logblocks * XFS_DFL_LOG_FACTOR);
> } else {
> - logblocks = MAX(logblocks,
> - MAX(XFS_DFL_LOG_SIZE,
> - min_logblocks * XFS_DFL_LOG_FACTOR));
> + /*
> + * With a 2GB max log size, default to maximum size
> + * at 4TB. This keeps the same ratio from the older
> + * max log size of 128M at 256GB fs size. IOWs,
> + * the ratio of fs size to log size is 2048:1.
> + */
> + logblocks = (dblocks << blocklog) / 2048;
> + logblocks = logblocks >> blocklog;
> + logblocks = MAX(min_logblocks, logblocks);
> }
> +
> + /* make sure the log fits wholly within an AG */
> + if (logblocks >= agsize)
> + logblocks = min_logblocks;
> +
> + /* and now clamp the size to the maximum supported size */
> logblocks = MIN(logblocks, XFS_MAX_LOG_BLOCKS);
> - if ((logblocks << blocklog) > XFS_MAX_LOG_BYTES) {
> + if ((logblocks << blocklog) > XFS_MAX_LOG_BYTES)
> logblocks = XFS_MAX_LOG_BYTES >> blocklog;
> - }
> +
> }
> validate_log_size(logblocks, blocklog, min_logblocks);
>
>
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