Mailing List Archive

commit 7050ccee978b77d94a622406dc3a181d876fbc2d
Author: Martin Blix Grydeland <martin@varnish-software.com>
Date: Thu Mar 19 15:17:45 2020 +0100

Repurpose OC_EF_REFD flag slightly

The OC_EF_REFD flag indicates whether expiry has a ref on the
OC. Previously, the flag was only gained during the call to
EXP_Insert. With this patch, and the helper function EXP_RefNewObjcore(),
the flag is gained while holding the objhead mutex during
HSH_Unbusy(). This enables the expiry functions to test on missing
OC_EF_REFD and quickly return without having to take the main expiry
mutex.

diff --git a/bin/varnishd/cache/cache_expire.c b/bin/varnishd/cache/cache_expire.c
index 67d5b85ba..12feff3da 100644
--- a/bin/varnishd/cache/cache_expire.c
+++ b/bin/varnishd/cache/cache_expire.c
@@ -105,10 +105,11 @@ exp_mail_it(struct objcore *oc, uint8_t cmds)
{
CHECK_OBJ_NOTNULL(oc, OBJCORE_MAGIC);
assert(oc->refcnt > 0);
+ AZ(cmds & OC_EF_REFD);

Lck_AssertHeld(&exphdl->mtx);

- if ((cmds | oc->exp_flags) & OC_EF_REFD) {
+ if (oc->exp_flags & OC_EF_REFD) {
if (!(oc->exp_flags & OC_EF_POSTED)) {
if (cmds & OC_EF_REMOVE)
VSTAILQ_INSERT_HEAD(&exphdl->inbox,
@@ -119,11 +120,30 @@ exp_mail_it(struct objcore *oc, uint8_t cmds)
VSC_C_main->exp_mailed++;
}
oc->exp_flags |= cmds | OC_EF_POSTED;
- AN(oc->exp_flags & OC_EF_REFD);
AZ(pthread_cond_signal(&exphdl->condvar));
}
}

+/*--------------------------------------------------------------------
+ * Setup a new ObjCore for control by expire. Should be called with the
+ * ObjHead locked by HSH_Unbusy(/HSH_Insert) (in private access).
+ */
+
+void
+EXP_RefNewObjcore(struct objcore *oc)
+{
+ CHECK_OBJ_NOTNULL(oc, OBJCORE_MAGIC);
+
+ Lck_AssertHeld(&oc->objhead->mtx);
+
+ AZ(oc->exp_flags);
+ assert(oc->refcnt >= 1);
+ oc->refcnt++;
+ oc->exp_flags |= OC_EF_REFD;
+}
+
+
+
/*--------------------------------------------------------------------
* Call EXP's attention to a an oc
*/
@@ -152,6 +172,10 @@ EXP_Insert(struct worker *wrk, struct objcore *oc)

CHECK_OBJ_NOTNULL(wrk, WORKER_MAGIC);
CHECK_OBJ_NOTNULL(oc, OBJCORE_MAGIC);
+
+ if (!(oc->exp_flags & OC_EF_REFD))
+ return;
+
assert(oc->refcnt >= 2);

AZ(oc->flags & OC_F_DYING);
@@ -159,7 +183,7 @@ EXP_Insert(struct worker *wrk, struct objcore *oc)
ObjSendEvent(wrk, oc, OEV_INSERT);
Lck_Lock(&exphdl->mtx);
AZ(oc->exp_flags & (OC_EF_INSERT | OC_EF_MOVE));
- exp_mail_it(oc, OC_EF_INSERT | OC_EF_REFD | OC_EF_MOVE);
+ exp_mail_it(oc, OC_EF_INSERT | OC_EF_MOVE);
Lck_Unlock(&exphdl->mtx);
}

diff --git a/bin/varnishd/cache/cache_hash.c b/bin/varnishd/cache/cache_hash.c
index 831572956..9fd1b5091 100644
--- a/bin/varnishd/cache/cache_hash.c
+++ b/bin/varnishd/cache/cache_hash.c
@@ -305,7 +305,7 @@ HSH_Insert(struct worker *wrk, const void *digest, struct objcore *oc,
objecthead. The new object inherits our objhead reference. */
oc->objhead = oh;
VTAILQ_INSERT_TAIL(&oh->objcs, oc, hsh_list);
- oc->refcnt++; // For EXP_Insert
+ EXP_RefNewObjcore(oc);
Lck_Unlock(&oh->mtx);

BAN_RefBan(oc, ban);
@@ -836,7 +836,7 @@ HSH_Unbusy(struct worker *wrk, struct objcore *oc)
assert(oh->refcnt > 0);
assert(oc->refcnt > 0);
if (!(oc->flags & OC_F_PRIVATE))
- oc->refcnt++; // For EXP_Insert
+ EXP_RefNewObjcore(oc); /* Takes a ref for expiry */
/* XXX: strictly speaking, we should sort in Date: order. */
VTAILQ_REMOVE(&oh->objcs, oc, hsh_list);
VTAILQ_INSERT_HEAD(&oh->objcs, oc, hsh_list);
@@ -846,8 +846,8 @@ HSH_Unbusy(struct worker *wrk, struct objcore *oc)
hsh_rush1(wrk, oh, &rush, HSH_RUSH_POLICY);
}
Lck_Unlock(&oh->mtx);
- if (!(oc->flags & OC_F_PRIVATE))
- EXP_Insert(wrk, oc);
+ EXP_Insert(wrk, oc); /* Does nothing unless EXP_RefNewObjcore was
+ * called */
hsh_rush2(wrk, &rush);
}

diff --git a/bin/varnishd/cache/cache_varnishd.h b/bin/varnishd/cache/cache_varnishd.h
index b0a6a1930..339a89ddd 100644
--- a/bin/varnishd/cache/cache_varnishd.h
+++ b/bin/varnishd/cache/cache_varnishd.h
@@ -165,6 +165,7 @@ void VDI_Init(void);
/* cache_exp.c */
vtim_real EXP_Ttl(const struct req *, const struct objcore *);
vtim_real EXP_Ttl_grace(const struct req *, const struct objcore *oc);
+void EXP_RefNewObjcore(struct objcore *);
void EXP_Insert(struct worker *wrk, struct objcore *oc);
void EXP_Remove(struct objcore *);

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