Date: Tue, 21 Nov 2017 12:38:13 -0500 From: Mark Johnston <markj@FreeBSD.org> To: Andre Albsmeier <andre@fbsd.e4m.org> Cc: freebsd-hackers@freebsd.org Subject: Re: gmirror synchronising is very slow due to frequent metadata updates Message-ID: <20171121173813.GB4126@raichu> In-Reply-To: <20171120053409.GA57536@gate> References: <20171119103241.GA20588@voyager> <20171120033828.GA1959@bish> <20171120053409.GA57536@gate>
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On Mon, Nov 20, 2017 at 06:34:09AM +0100, Andre Albsmeier wrote:
> On Sun, 19-Nov-2017 at 22:38:28 -0500, Mark Johnston wrote:
> > We should probably decrease the update interval based on the size of a
> > mirror. For mirrors larger than say, 1GB, we might just update the
> > metadata block once per 1% of the synchronization operation's progress.
>
> I think best would be to have it updated every <whatever> seconds.
> I think of very fast or very slow drives, or drives which are used
> heavily during rebuild (where the effective rebuild speed is quite
> low)...
I think that's reasonable. Could you give the patch below a try? It adds
a sysctl which configures the frequency of metadata updates during
synchronization. It'd be nice to be able to specify this parameter (as
well as idletime) on a per-gmirror basis, with the default value still
being taken from the sysctl, but that can be implemented separately.
diff --git a/sys/geom/mirror/g_mirror.c b/sys/geom/mirror/g_mirror.c
index 4a5f542c1de5..47d11f3ce465 100644
--- a/sys/geom/mirror/g_mirror.c
+++ b/sys/geom/mirror/g_mirror.c
@@ -69,6 +69,10 @@ SYSCTL_UINT(_kern_geom_mirror, OID_AUTO, disconnect_on_failure, CTLFLAG_RWTUN,
static u_int g_mirror_syncreqs = 2;
SYSCTL_UINT(_kern_geom_mirror, OID_AUTO, sync_requests, CTLFLAG_RDTUN,
&g_mirror_syncreqs, 0, "Parallel synchronization I/O requests.");
+static u_int g_mirror_sync_period = 5;
+SYSCTL_UINT(_kern_geom_mirror, OID_AUTO, sync_update_period, CTLFLAG_RWTUN,
+ &g_mirror_sync_period, 0,
+ "Metadata update period during synchroniztion, in seconds");
#define MSLEEP(ident, mtx, priority, wmesg, timeout) do { \
G_MIRROR_DEBUG(4, "%s: Sleeping %p.", __func__, (ident)); \
@@ -463,6 +467,7 @@ g_mirror_init_disk(struct g_mirror_softc *sc, struct g_provider *pp,
disk->d_sync.ds_consumer = NULL;
disk->d_sync.ds_offset = md->md_sync_offset;
disk->d_sync.ds_offset_done = md->md_sync_offset;
+ disk->d_sync.ds_update_ts = time_uptime;
disk->d_genid = md->md_genid;
disk->d_sync.ds_syncid = md->md_syncid;
if (errorp != NULL)
@@ -1457,10 +1462,11 @@ g_mirror_sync_request(struct bio *bp)
if (bp != NULL && bp->bio_offset < offset)
offset = bp->bio_offset;
}
- if (sync->ds_offset_done + (MAXPHYS * 100) < offset) {
- /* Update offset_done on every 100 blocks. */
+ if (g_mirror_sync_period > 0 &&
+ time_uptime - sync->ds_update_ts > g_mirror_sync_period) {
sync->ds_offset_done = offset;
g_mirror_update_metadata(disk);
+ sync->ds_update_ts = time_uptime;
}
return;
}
diff --git a/sys/geom/mirror/g_mirror.h b/sys/geom/mirror/g_mirror.h
index 3b9664035c98..be46f7b43e4c 100644
--- a/sys/geom/mirror/g_mirror.h
+++ b/sys/geom/mirror/g_mirror.h
@@ -108,6 +108,7 @@ struct g_mirror_disk_sync {
off_t ds_offset; /* Offset of next request to send. */
off_t ds_offset_done; /* Offset of already synchronized
region. */
+ time_t ds_update_ts; /* Time of last metadata update. */
u_int ds_syncid; /* Disk's synchronization ID. */
u_int ds_inflight; /* Number of in-flight sync requests. */
struct bio **ds_bios; /* BIOs for synchronization I/O. */
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