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authorSeth Jennings <sjenning@linux.vnet.ibm.com>2011-10-12 14:41:00 -0500
committerGreg Kroah-Hartman <gregkh@suse.de>2011-10-17 15:24:11 -0700
commit00bf256011d362e7d61824f3cda8514f5d48585d (patch)
treec76261e9e4d023628673253f74648504295274ed /drivers/staging/zcache
parent3b769edd58371fb70417c3f43c6d4a2da075703a (diff)
staging: zcache: remove zcache_direct_reclaim_lock
zcache_do_preload() currently does a spin_trylock() on the zcache_direct_reclaim_lock. Holding this lock intends to prevent shrink_zcache_memory() from evicting zbud pages as a result of a preload. However, it also prevents two threads from executing zcache_do_preload() at the same time. The first thread will obtain the lock and the second thread's spin_trylock() will fail (an aborted preload) causing the page to be either lost (cleancache) or pushed out to the swap device (frontswap). It also doesn't ensure that the call to shrink_zcache_memory() is on the same thread as the call to zcache_do_preload(). Additional, there is no need for this mechanism because all zcache_do_preload() calls that come down from cleancache already have PF_MEMALLOC set in the process flags which prevents direct reclaim in the memory manager. If the zcache_do_preload() call is done from the frontswap path, we _want_ reclaim to be done (which it isn't right now). This patch removes the zcache_direct_reclaim_lock and related statistics in zcache. Based on v3.1-rc8 Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com> Reviewed-by: Dave Hansen <dave@linux.vnet.ibm.com> Acked-by: Dan Magenheimer <dan.magenheimer@oracle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/staging/zcache')
-rw-r--r--drivers/staging/zcache/zcache-main.c31
1 files changed, 4 insertions, 27 deletions
diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
index 22b0a7506496..3768bf2e8d91 100644
--- a/drivers/staging/zcache/zcache-main.c
+++ b/drivers/staging/zcache/zcache-main.c
@@ -962,15 +962,6 @@ out:
static unsigned long zcache_failed_get_free_pages;
static unsigned long zcache_failed_alloc;
static unsigned long zcache_put_to_flush;
-static unsigned long zcache_aborted_preload;
-static unsigned long zcache_aborted_shrink;
-
-/*
- * Ensure that memory allocation requests in zcache don't result
- * in direct reclaim requests via the shrinker, which would cause
- * an infinite loop. Maybe a GFP flag would be better?
- */
-static DEFINE_SPINLOCK(zcache_direct_reclaim_lock);
/*
* for now, used named slabs so can easily track usage; later can
@@ -1009,10 +1000,6 @@ static int zcache_do_preload(struct tmem_pool *pool)
goto out;
if (unlikely(zcache_obj_cache == NULL))
goto out;
- if (!spin_trylock(&zcache_direct_reclaim_lock)) {
- zcache_aborted_preload++;
- goto out;
- }
preempt_disable();
kp = &__get_cpu_var(zcache_preloads);
while (kp->nr < ARRAY_SIZE(kp->objnodes)) {
@@ -1021,7 +1008,7 @@ static int zcache_do_preload(struct tmem_pool *pool)
ZCACHE_GFP_MASK);
if (unlikely(objnode == NULL)) {
zcache_failed_alloc++;
- goto unlock_out;
+ goto out;
}
preempt_disable();
kp = &__get_cpu_var(zcache_preloads);
@@ -1034,13 +1021,13 @@ static int zcache_do_preload(struct tmem_pool *pool)
obj = kmem_cache_alloc(zcache_obj_cache, ZCACHE_GFP_MASK);
if (unlikely(obj == NULL)) {
zcache_failed_alloc++;
- goto unlock_out;
+ goto out;
}
page = (void *)__get_free_page(ZCACHE_GFP_MASK);
if (unlikely(page == NULL)) {
zcache_failed_get_free_pages++;
kmem_cache_free(zcache_obj_cache, obj);
- goto unlock_out;
+ goto out;
}
preempt_disable();
kp = &__get_cpu_var(zcache_preloads);
@@ -1053,8 +1040,6 @@ static int zcache_do_preload(struct tmem_pool *pool)
else
free_page((unsigned long)page);
ret = 0;
-unlock_out:
- spin_unlock(&zcache_direct_reclaim_lock);
out:
return ret;
}
@@ -1429,8 +1414,6 @@ ZCACHE_SYSFS_RO(evicted_buddied_pages);
ZCACHE_SYSFS_RO(failed_get_free_pages);
ZCACHE_SYSFS_RO(failed_alloc);
ZCACHE_SYSFS_RO(put_to_flush);
-ZCACHE_SYSFS_RO(aborted_preload);
-ZCACHE_SYSFS_RO(aborted_shrink);
ZCACHE_SYSFS_RO(compress_poor);
ZCACHE_SYSFS_RO(mean_compress_poor);
ZCACHE_SYSFS_RO_ATOMIC(zbud_curr_raw_pages);
@@ -1472,8 +1455,6 @@ static struct attribute *zcache_attrs[] = {
&zcache_failed_get_free_pages_attr.attr,
&zcache_failed_alloc_attr.attr,
&zcache_put_to_flush_attr.attr,
- &zcache_aborted_preload_attr.attr,
- &zcache_aborted_shrink_attr.attr,
&zcache_zbud_unbuddied_list_counts_attr.attr,
&zcache_zbud_cumul_chunk_counts_attr.attr,
&zcache_zv_curr_dist_counts_attr.attr,
@@ -1513,11 +1494,7 @@ static int shrink_zcache_memory(struct shrinker *shrink,
if (!(gfp_mask & __GFP_FS))
/* does this case really need to be skipped? */
goto out;
- if (spin_trylock(&zcache_direct_reclaim_lock)) {
- zbud_evict_pages(nr);
- spin_unlock(&zcache_direct_reclaim_lock);
- } else
- zcache_aborted_shrink++;
+ zbud_evict_pages(nr);
}
ret = (int)atomic_read(&zcache_zbud_curr_raw_pages);
out: