Recompression iterates through all the registered secondary
compression algorithms in order of their priorities so that
we have higher chances of finding the algorithm that compresses
a particular page. This, however, may not always be best
approach and sometimes we may want to limit recompression to
only one particular algorithm. For instance, when a higher
priority algorithm uses too much power and device has a
relatively low battery level we may want to limit recompression
to use only a lower priority algorithm, which uses less power.
Introduce algo= parameter support to recompression sysfs knob
so that user-sapce can request recompression with particular
algorithm only:
echo "type=idle algo=zstd" > /sys/block/zramX/recompress
Signed-off-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
---
drivers/block/zram/zram_drv.c | 54 +++++++++++++++++++++++++++++------
drivers/block/zram/zram_drv.h | 1 +
2 files changed, 46 insertions(+), 9 deletions(-)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 67b58f2255db..89d25f60b33e 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1677,6 +1677,7 @@ static int zram_recompress(struct zram *zram, u32 index, struct page *page,
unsigned int comp_len_new;
unsigned int class_index_old;
unsigned int class_index_new;
+ u32 num_recomps = 0;
void *src, *dst;
int ret;
@@ -1711,6 +1712,7 @@ static int zram_recompress(struct zram *zram, u32 index, struct page *page,
if (prio <= zram_get_priority(zram, index))
continue;
+ num_recomps++;
zstrm = zcomp_stream_get(zram->comps[prio]);
src = kmap_atomic(page);
ret = zcomp_compress(zstrm, src, &comp_len_new);
@@ -1743,13 +1745,19 @@ static int zram_recompress(struct zram *zram, u32 index, struct page *page,
if (!zstrm)
return 0;
- /*
- * All secondary algorithms failed to re-compress the page in a way
- * that would save memory, mark the object as incompressible so that
- * we will not try to compress it again.
- */
if (class_index_new >= class_index_old) {
- zram_set_flag(zram, index, ZRAM_INCOMPRESSIBLE);
+ /*
+ * Secondary algorithms failed to re-compress the page
+ * in a way that would save memory, mark the object as
+ * incompressible so that we will not try to compress
+ * it again.
+ *
+ * We need to make sure that all secondary algorithms have
+ * failed, so we test if the number of recompressions matches
+ * the number of active secondary algorithms.
+ */
+ if (num_recomps == zram->num_active_comps - 1)
+ zram_set_flag(zram, index, ZRAM_INCOMPRESSIBLE);
return 0;
}
@@ -1798,10 +1806,11 @@ static ssize_t recompress_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t len)
{
+ u32 prio = ZRAM_SECONDARY_COMP, prio_max = ZRAM_MAX_COMPS;
struct zram *zram = dev_to_zram(dev);
- u32 mode = 0, threshold = 0, prio = ZRAM_SECONDARY_COMP;
unsigned long nr_pages = zram->disksize >> PAGE_SHIFT;
- char *args, *param, *val;
+ char *args, *param, *val, *algo = NULL;
+ u32 mode = 0, threshold = 0;
unsigned long index;
struct page *page;
ssize_t ret;
@@ -1833,6 +1842,11 @@ static ssize_t recompress_store(struct device *dev,
return ret;
continue;
}
+
+ if (!strcmp(param, "algo")) {
+ algo = val;
+ continue;
+ }
}
if (threshold >= PAGE_SIZE)
@@ -1844,6 +1858,26 @@ static ssize_t recompress_store(struct device *dev,
goto release_init_lock;
}
+ if (algo) {
+ bool found = false;
+
+ for (; prio < ZRAM_MAX_COMPS; prio++) {
+ if (!zram->comp_algs[prio])
+ continue;
+
+ if (!strcmp(zram->comp_algs[prio], algo)) {
+ prio_max = min(prio + 1, ZRAM_MAX_COMPS);
+ found = true;
+ break;
+ }
+ }
+
+ if (!found) {
+ ret = -EINVAL;
+ goto release_init_lock;
+ }
+ }
+
page = alloc_page(GFP_KERNEL);
if (!page) {
ret = -ENOMEM;
@@ -1874,7 +1908,7 @@ static ssize_t recompress_store(struct device *dev,
goto next;
err = zram_recompress(zram, index, page, threshold,
- prio, ZRAM_MAX_COMPS);
+ prio, prio_max);
next:
zram_slot_unlock(zram, index);
if (err) {
@@ -2110,6 +2144,7 @@ static void zram_destroy_comps(struct zram *zram)
if (!comp)
continue;
zcomp_destroy(comp);
+ zram->num_active_comps--;
}
}
@@ -2177,6 +2212,7 @@ static ssize_t disksize_store(struct device *dev,
}
zram->comps[prio] = comp;
+ zram->num_active_comps++;
}
zram->disksize = disksize;
set_capacity_and_notify(zram->disk, zram->disksize >> SECTOR_SHIFT);
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index b80faae76835..473325415a74 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -125,6 +125,7 @@ struct zram {
*/
u64 disksize; /* bytes */
const char *comp_algs[ZRAM_MAX_COMPS];
+ s8 num_active_comps;
/*
* zram is claimed so open request will be failed
*/
--
2.38.1.431.g37b22c650d-goog
