Message ID | 1337287349-7664-1-git-send-email-josh.durgin@inktank.com |
---|---|
State | New |
Headers | show |
Am 17.05.2012 22:42, schrieb Josh Durgin: > Writeback caching was added in Ceph 0.46, and writethrough will be in > 0.47. These are controlled by general config options, so there's no > need to check for librbd version. > > Signed-off-by: Josh Durgin <josh.durgin@inktank.com> Thanks, applied to the block-next branch for 1.2. Kevin
Il 17/05/2012 22:42, Josh Durgin ha scritto: > + * Fallback to more conservative semantics if setting cache > + * options fails. Ignore errors from setting rbd_cache because the > + * only possible error is that the option does not exist, and > + * librbd defaults to no caching. If write through caching cannot > + * be set up, fall back to no caching. > + */ > + if (flags & BDRV_O_NOCACHE) { > + rados_conf_set(s->cluster, "rbd_cache", "false"); > + } else { > + rados_conf_set(s->cluster, "rbd_cache", "true"); > + if (!(flags & BDRV_O_CACHE_WB)) { > + r = rados_conf_set(s->cluster, "rbd_cache_max_dirty", "0"); > + if (r < 0) { > + rados_conf_set(s->cluster, "rbd_cache", "false"); > + } > + } > + } Last time I looked at ceph, rbd_flush was not a full flush of the cache; it only ensured that the pending requests were sent. So my questions are: 1) has this changed? does rbd_flush now flush dirty items when rbd_cache_max_dirty > 0? 2) should the usage of a cache be conditional on LIBRBD_VERSION_CODE >= LIBRBD_VERSION(0, 1, 1)? Thanks, Paolo
On 05/22/2012 02:18 AM, Paolo Bonzini wrote: > Il 17/05/2012 22:42, Josh Durgin ha scritto: >> + * Fallback to more conservative semantics if setting cache >> + * options fails. Ignore errors from setting rbd_cache because the >> + * only possible error is that the option does not exist, and >> + * librbd defaults to no caching. If write through caching cannot >> + * be set up, fall back to no caching. >> + */ >> + if (flags& BDRV_O_NOCACHE) { >> + rados_conf_set(s->cluster, "rbd_cache", "false"); >> + } else { >> + rados_conf_set(s->cluster, "rbd_cache", "true"); >> + if (!(flags& BDRV_O_CACHE_WB)) { >> + r = rados_conf_set(s->cluster, "rbd_cache_max_dirty", "0"); >> + if (r< 0) { >> + rados_conf_set(s->cluster, "rbd_cache", "false"); >> + } >> + } >> + } > > Last time I looked at ceph, rbd_flush was not a full flush of the cache; > it only ensured that the pending requests were sent. So my questions are: I'm not sure which version you were looking at, but this hasn't been the case since caching was implemented. I don't think it was ever the case, actually. rbd_flush has always waited for pending I/Os to complete (be on disk on all replicas), not just be in flight. If you're interested in the current implementation, you can see: src/librbd.cc: librbd::flush() which goes into: src/osdc/ObjectCacher.cc: ObjectCacher::commit_set() or src/librados/IoCtxImpl.cc: IoCtxImpl::flush_aio_writes() > 1) has this changed? does rbd_flush now flush dirty items when > rbd_cache_max_dirty> 0? The rbd_cache_* options did not exist before 0.46. > 2) should the usage of a cache be conditional on LIBRBD_VERSION_CODE>= > LIBRBD_VERSION(0, 1, 1)? It doesn't matter if you use an older version because the non-existent options don't have any effect. Thanks, Josh
diff --git a/block/rbd.c b/block/rbd.c index 1280d66..eebc334 100644 --- a/block/rbd.c +++ b/block/rbd.c @@ -476,6 +476,25 @@ static int qemu_rbd_open(BlockDriverState *bs, const char *filename, int flags) s->snap = g_strdup(snap_buf); } + /* + * Fallback to more conservative semantics if setting cache + * options fails. Ignore errors from setting rbd_cache because the + * only possible error is that the option does not exist, and + * librbd defaults to no caching. If write through caching cannot + * be set up, fall back to no caching. + */ + if (flags & BDRV_O_NOCACHE) { + rados_conf_set(s->cluster, "rbd_cache", "false"); + } else { + rados_conf_set(s->cluster, "rbd_cache", "true"); + if (!(flags & BDRV_O_CACHE_WB)) { + r = rados_conf_set(s->cluster, "rbd_cache_max_dirty", "0"); + if (r < 0) { + rados_conf_set(s->cluster, "rbd_cache", "false"); + } + } + } + if (strstr(conf, "conf=") == NULL) { /* try default location, but ignore failure */ rados_conf_read_file(s->cluster, NULL);
Writeback caching was added in Ceph 0.46, and writethrough will be in 0.47. These are controlled by general config options, so there's no need to check for librbd version. Signed-off-by: Josh Durgin <josh.durgin@inktank.com> --- block/rbd.c | 19 +++++++++++++++++++ 1 files changed, 19 insertions(+), 0 deletions(-)