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varnishcache
varnish-cache
Commits
4d8aa0c3
Commit
4d8aa0c3
authored
May 03, 2016
by
Nils Goroll
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ban lurker: When loosing the lock race to lookup, continue with other objects if possible
parent
4c36d7ca
Changes
1
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1 changed file
with
57 additions
and
17 deletions
+57
-17
cache_ban_lurker.c
bin/varnishd/cache/cache_ban_lurker.c
+57
-17
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bin/varnishd/cache/cache_ban_lurker.c
View file @
4d8aa0c3
...
...
@@ -36,7 +36,8 @@
#include "hash/hash_slinger.h"
#include "vtim.h"
static
struct
objcore
oc_marker
=
{
.
magic
=
OBJCORE_MAGIC
,
};
static
struct
objcore
oc_mark_cnt
=
{
.
magic
=
OBJCORE_MAGIC
,
};
static
struct
objcore
oc_mark_end
=
{
.
magic
=
OBJCORE_MAGIC
,
};
static
unsigned
ban_batch
;
static
unsigned
ban_generation
;
...
...
@@ -110,23 +111,56 @@ ban_cleantail(const struct ban *victim)
* makes most sense in HSH_Lookup(), but we come the other way.
* We optimistically try to get them the other way, and get out of
* the way if that fails, and retry again later.
*
* To avoid hammering on contested ocs, we first move those behind a marker
* once. When we only have contested ocs left, we stop moving them around and
* re-try them in order.
*/
static
struct
objcore
*
ban_lurker_getfirst
(
struct
vsl_log
*
vsl
,
struct
ban
*
bt
)
{
struct
objhead
*
oh
;
struct
objcore
*
oc
;
struct
objcore
*
oc
,
*
noc
;
int
move_oc
=
1
;
while
(
1
)
{
Lck_Lock
(
&
ban_mtx
);
oc
=
VTAILQ_FIRST
(
&
bt
->
objcore
);
while
(
1
)
{
CHECK_OBJ_NOTNULL
(
oc
,
OBJCORE_MAGIC
);
if
(
oc
==
&
oc_marker
)
{
VTAILQ_REMOVE
(
&
bt
->
objcore
,
oc
,
ban_list
);
if
(
oc
==
&
oc_mark_cnt
)
{
if
(
VTAILQ_NEXT
(
oc
,
ban_list
)
==
&
oc_mark_end
)
{
/* done with this ban's oc list */
VTAILQ_REMOVE
(
&
bt
->
objcore
,
&
oc_mark_cnt
,
ban_list
);
VTAILQ_REMOVE
(
&
bt
->
objcore
,
&
oc_mark_end
,
ban_list
);
oc
=
NULL
;
break
;
}
oc
=
VTAILQ_NEXT
(
oc
,
ban_list
);
CHECK_OBJ_NOTNULL
(
oc
,
OBJCORE_MAGIC
);
move_oc
=
0
;
}
else
if
(
oc
==
&
oc_mark_end
)
{
assert
(
move_oc
==
0
);
/* hold off to give lookup a chance and reiterate */
Lck_Unlock
(
&
ban_mtx
);
return
(
NULL
);
VSC_C_main
->
bans_lurker_contention
++
;
VSL_Flush
(
vsl
,
0
);
VTIM_sleep
(
cache_param
->
ban_lurker_holdoff
);
Lck_Lock
(
&
ban_mtx
);
oc
=
VTAILQ_FIRST
(
&
bt
->
objcore
);
assert
(
oc
==
&
oc_mark_cnt
);
continue
;
}
assert
(
oc
!=
&
oc_mark_cnt
);
assert
(
oc
!=
&
oc_mark_end
);
oh
=
oc
->
objhead
;
CHECK_OBJ_NOTNULL
(
oh
,
OBJHEAD_MAGIC
);
if
(
!
Lck_Trylock
(
&
oh
->
mtx
))
{
...
...
@@ -135,24 +169,28 @@ ban_lurker_getfirst(struct vsl_log *vsl, struct ban *bt)
}
else
{
/*
* We got the lock, and the oc is not being
* dismantled under our feet
.
* dismantled under our feet
- grab a ref
*/
AZ
(
oc
->
flags
&
OC_F_BUSY
);
oc
->
refcnt
+=
1
;
VTAILQ_REMOVE
(
&
bt
->
objcore
,
oc
,
ban_list
);
VTAILQ_INSERT_TAIL
(
&
bt
->
objcore
,
oc
,
ban_list
);
Lck_Unlock
(
&
oh
->
mtx
);
Lck_Unlock
(
&
ban_mtx
);
break
;
}
}
/* Try again, later */
Lck_Unlock
(
&
ban_mtx
);
VSC_C_main
->
bans_lurker_contention
++
;
VSL_Flush
(
vsl
,
0
);
VTIM_sleep
(
cache_param
->
ban_lurker_holdoff
);
noc
=
VTAILQ_NEXT
(
oc
,
ban_list
);
if
(
move_oc
)
{
/* contested ocs go between the two markers */
VTAILQ_REMOVE
(
&
bt
->
objcore
,
oc
,
ban_list
);
VTAILQ_INSERT_BEFORE
(
&
oc_mark_end
,
oc
,
ban_list
);
}
oc
=
noc
;
}
Lck_Unlock
(
&
ban_mtx
);
return
(
oc
);
}
...
...
@@ -166,12 +204,14 @@ ban_lurker_test_ban(struct worker *wrk, struct vsl_log *vsl, struct ban *bt,
int
i
;
/*
* First see if there is anything to do, and if so, insert marker
* First see if there is anything to do, and if so, insert marker
s
*/
Lck_Lock
(
&
ban_mtx
);
oc
=
VTAILQ_FIRST
(
&
bt
->
objcore
);
if
(
oc
!=
NULL
)
VTAILQ_INSERT_TAIL
(
&
bt
->
objcore
,
&
oc_marker
,
ban_list
);
if
(
oc
!=
NULL
)
{
VTAILQ_INSERT_TAIL
(
&
bt
->
objcore
,
&
oc_mark_cnt
,
ban_list
);
VTAILQ_INSERT_TAIL
(
&
bt
->
objcore
,
&
oc_mark_end
,
ban_list
);
}
Lck_Unlock
(
&
ban_mtx
);
if
(
oc
==
NULL
)
return
;
...
...
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