Author: davide
Date: Mon Aug 25 17:06:18 2014
New Revision: 270588
URL: http://svnweb.freebsd.org/changeset/base/270588
Log:
Rather than using an hardcoded reclaim age, rely on an LRU-like approach
for dirhash cache, setting a target percent to reclaim (exposed via
SYSCTL). This allows to always make some amount of progress keeping the
maximum
reclaim age dynamic.
Tested by: pho
Reviewed by: jhb
Modified:
head/sys/ufs/ufs/ufs_dirhash.c
Modified: head/sys/ufs/ufs/ufs_dirhash.c
==============================================================================
--- head/sys/ufs/ufs/ufs_dirhash.c Mon Aug 25 16:56:33 2014
(r270587)
+++ head/sys/ufs/ufs/ufs_dirhash.c Mon Aug 25 17:06:18 2014
(r270588)
@@ -85,10 +85,10 @@ SYSCTL_INT(_vfs_ufs, OID_AUTO, dirhash_d
static int ufs_dirhashlowmemcount = 0;
SYSCTL_INT(_vfs_ufs, OID_AUTO, dirhash_lowmemcount, CTLFLAG_RD,
&ufs_dirhashlowmemcount, 0, "number of times low memory hook called");
-static int ufs_dirhashreclaimage = 60;
-SYSCTL_INT(_vfs_ufs, OID_AUTO, dirhash_reclaimage, CTLFLAG_RW,
- &ufs_dirhashreclaimage, 0,
- "max time in seconds of hash inactivity before deletion in low VM events");
+static int ufs_dirhash_reclaimperc = 10;
+SYSCTL_INT(_vfs_ufs, OID_AUTO, dirhash_reclaimperc, CTLFLAG_RW,
+ &ufs_dirhash_reclaimperc, 0,
+ "percentage of dirhash cache to be removed in low VM events");
static int ufsdirhash_hash(struct dirhash *dh, char *name, int namelen);
@@ -1247,45 +1247,28 @@ static void
ufsdirhash_lowmem()
{
struct dirhash *dh, *dh_temp;
- int memfreed = 0;
- /*
- * Will free a *minimum* of 10% of the dirhash, but possibly much
- * more (depending on dirhashreclaimage). System with large dirhashes
- * probably also need a much larger dirhashreclaimage.
- * XXX: this percentage may need to be adjusted.
- */
- int memwanted = ufs_dirhashmem / 10;
+ int memfreed, memwanted;
ufs_dirhashlowmemcount++;
+ memfreed = 0;
+ memwanted = ufs_dirhashmem / ufs_dirhash_reclaimperc;
DIRHASHLIST_LOCK();
- /*
- * Delete dirhashes not used for more than ufs_dirhashreclaimage
- * seconds. If we can't get a lock on the dirhash, it will be skipped.
- */
- TAILQ_FOREACH_SAFE(dh, &ufsdirhash_list, dh_list, dh_temp) {
- if (!sx_try_xlock(&dh->dh_lock))
- continue;
- if (time_second - dh->dh_lastused > ufs_dirhashreclaimage)
- memfreed += ufsdirhash_destroy(dh);
- /* Unlock if we didn't delete the dirhash */
- else
- ufsdirhash_release(dh);
- }
- /*
- * If not enough memory was freed, keep deleting hashes from the head
- * of the dirhash list. The ones closest to the head should be the
- * oldest.
+ /*
+ * Reclaim up to memwanted from the oldest dirhashes. This will allow
+ * us to make some progress when the system is running out of memory
+ * without compromising the dinamicity of maximum age. If the situation
+ * does not improve lowmem will be eventually retriggered and free some
+ * other entry in the cache. The entries on the head of the list should
+ * be the oldest. If during list traversal we can't get a lock on the
+ * dirhash, it will be skipped.
*/
- if (memfreed < memwanted) {
- TAILQ_FOREACH_SAFE(dh, &ufsdirhash_list, dh_list, dh_temp) {
- if (!sx_try_xlock(&dh->dh_lock))
- continue;
+ TAILQ_FOREACH_SAFE(dh, &ufsdirhash_list, dh_list, dh_temp) {
+ if (sx_try_xlock(&dh->dh_lock))
memfreed += ufsdirhash_destroy(dh);
- if (memfreed >= memwanted)
- break;
- }
+ if (memfreed >= memwanted)
+ break;
}
DIRHASHLIST_UNLOCK();
}
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