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Make use of GEOM Gate direct reads feature. This allows HAST to serve

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reads with native speed of the underlying provider.
There are three situations when direct reads are not used:
1. Data is being synchronized and synchronization source is the secondary
   node, which means secondary node has more recent data and we should read
   from it.
2. Local read failed and we have to try to read from the secondary node.
3. Local component is unavailable and all I/O requests are served from the
   secondary node.

Sponsored by:	Panzura, http://www.panzura.com
MFC after:	1 month
This commit is contained in:
pjd 2012-07-04 20:20:48 +00:00
parent 5ef9eb30da
commit 1fb1092d75
1 changed files with 31 additions and 1 deletions
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32
sbin/hastd/primary.c
View File

@ -543,6 +543,27 @@ primary_connect(struct hast_resource *res, struct proto_conn **connp)
return (0);
}
/*
* Function instructs GEOM_GATE to handle reads directly from within the kernel.
*/
static void
enable_direct_reads(struct hast_resource *res)
{
struct g_gate_ctl_modify ggiomodify;
bzero(&ggiomodify, sizeof(ggiomodify));
ggiomodify.gctl_version = G_GATE_VERSION;
ggiomodify.gctl_unit = res->hr_ggateunit;
ggiomodify.gctl_modify = GG_MODIFY_READPROV | GG_MODIFY_READOFFSET;
strlcpy(ggiomodify.gctl_readprov, res->hr_localpath,
sizeof(ggiomodify.gctl_readprov));
ggiomodify.gctl_readoffset = res->hr_localoff;
if (ioctl(res->hr_ggatefd, G_GATE_CMD_MODIFY, &ggiomodify) == 0)
pjdlog_debug(1, "Direct reads enabled.");
else
pjdlog_errno(LOG_WARNING, "Failed to enable direct reads");
}
static int
init_remote(struct hast_resource *res, struct proto_conn **inp,
@ -692,6 +713,8 @@ init_remote(struct hast_resource *res, struct proto_conn **inp,
res->hr_secondary_localcnt = nv_get_uint64(nvin, "localcnt");
res->hr_secondary_remotecnt = nv_get_uint64(nvin, "remotecnt");
res->hr_syncsrc = nv_get_uint8(nvin, "syncsrc");
if (res->hr_syncsrc == HAST_SYNCSRC_PRIMARY)
enable_direct_reads(res);
if (nv_exists(nvin, "virgin")) {
/*
* Secondary was reinitialized, bump localcnt if it is 0 as
@ -1789,13 +1812,14 @@ sync_thread(void *arg __unused)
struct timeval tstart, tend, tdiff;
unsigned int ii, ncomp, ncomps;
off_t offset, length, synced;
bool dorewind;
bool dorewind, directreads;
int syncext;
ncomps = HAST_NCOMPONENTS;
dorewind = true;
synced = 0;
offset = -1;
directreads = false;
for (;;) {
mtx_lock(&sync_lock);
@ -1867,6 +1891,8 @@ sync_thread(void *arg __unused)
event_send(res, EVENT_SYNCDONE);
}
mtx_lock(&metadata_lock);
if (res->hr_syncsrc == HAST_SYNCSRC_SECONDARY)
directreads = true;
res->hr_syncsrc = HAST_SYNCSRC_UNDEF;
res->hr_primary_localcnt =
res->hr_secondary_remotecnt;
@ -1880,6 +1906,10 @@ sync_thread(void *arg __unused)
mtx_unlock(&metadata_lock);
}
rw_unlock(&hio_remote_lock[ncomp]);
if (directreads) {
directreads = false;
enable_direct_reads(res);
}
continue;
}
pjdlog_debug(2, "sync: Taking free request.");