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zram: add max_pages param to recompression

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Introduce "max_pages" param to recompress device attribute which sets an
upper limit on the number of entries (pages) zram attempts to recompress
(in this particular recompression call).  S/W recompression can be quite
expensive so limiting the number of pages recompress touches can be quite
helpful.

Link: https://lkml.kernel.org/r/20240329094050.2815699-1-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Brian Geffon <bgeffon@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Sergey Senozhatsky 2024-03-29 18:39:41 +09:00 committed by Andrew Morton
parent ba42b524a0
commit 34efe1c3b6
2 changed files with 33 additions and 3 deletions
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5
Documentation/admin-guide/blockdev/zram.rst
View File

@ -466,6 +466,11 @@ of equal or greater size:::
#recompress idle pages larger than 2000 bytes
echo "type=idle threshold=2000" > /sys/block/zramX/recompress
It is also possible to limit the number of pages zram re-compression will
attempt to recompress:::
echo "type=huge_idle max_pages=42" > /sys/block/zramX/recompress
Recompression of idle pages requires memory tracking.
During re-compression for every page, that matches re-compression criteria,

31
drivers/block/zram/zram_drv.c
View File

@ -1568,7 +1568,8 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
* Corresponding ZRAM slot should be locked.
*/
static int zram_recompress(struct zram *zram, u32 index, struct page *page,
u32 threshold, u32 prio, u32 prio_max)
u64 *num_recomp_pages, u32 threshold, u32 prio,
u32 prio_max)
{
struct zcomp_strm *zstrm = NULL;
unsigned long handle_old;
@ -1645,6 +1646,15 @@ static int zram_recompress(struct zram *zram, u32 index, struct page *page,
if (!zstrm)
return 0;
/*
* Decrement the limit (if set) on pages we can recompress, even
* when current recompression was unsuccessful or did not compress
* the page below the threshold, because we still spent resources
* on it.
*/
if (*num_recomp_pages)
*num_recomp_pages -= 1;
if (class_index_new >= class_index_old) {
/*
* Secondary algorithms failed to re-compress the page
@ -1710,6 +1720,7 @@ static ssize_t recompress_store(struct device *dev,
struct zram *zram = dev_to_zram(dev);
unsigned long nr_pages = zram->disksize >> PAGE_SHIFT;
char *args, *param, *val, *algo = NULL;
u64 num_recomp_pages = ULLONG_MAX;
u32 mode = 0, threshold = 0;
unsigned long index;
struct page *page;
@ -1732,6 +1743,17 @@ static ssize_t recompress_store(struct device *dev,
continue;
}
if (!strcmp(param, "max_pages")) {
/*
* Limit the number of entries (pages) we attempt to
* recompress.
*/
ret = kstrtoull(val, 10, &num_recomp_pages);
if (ret)
return ret;
continue;
}
if (!strcmp(param, "threshold")) {
/*
* We will re-compress only idle objects equal or
@ -1788,6 +1810,9 @@ static ssize_t recompress_store(struct device *dev,
for (index = 0; index < nr_pages; index++) {
int err = 0;
if (!num_recomp_pages)
break;
zram_slot_lock(zram, index);
if (!zram_allocated(zram, index))
@ -1807,8 +1832,8 @@ static ssize_t recompress_store(struct device *dev,
zram_test_flag(zram, index, ZRAM_INCOMPRESSIBLE))
goto next;
err = zram_recompress(zram, index, page, threshold,
prio, prio_max);
err = zram_recompress(zram, index, page, &num_recomp_pages,
threshold, prio, prio_max);
next:
zram_slot_unlock(zram, index);
if (err) {